This tutorial gives brief illustrations of the calculator’s main features; complete descriptions of these features, as well as descriptions of many terms that may be unfamiliar, are given in the Sun/Moon Calculator Reference.
Contents
Setting the Location
Basic Calculations: Rise/Set Times and Sun and Moon Positions
Getting the Times of Rise and Set for More Than One Day
Getting Sun and Moon Positions for Times Throughout the Day
Active and Inactive Inputs
Data Entry and Validation
Finding Dates on Which the Sun or Moon Rises or Sets in a Particular Direction
Finding Dates on Which the Moon Rises Close to Sunset
Finding Dates of “Supermoons”
Finding Dates on Which the Sun or Moon Is Near a Natural or Man-Made Feature
Example 2: A Natural Setting with Broad Alignment Criteria
Example 3: A Natural Setting with Many Possible Camera Positions
Example 5: Finding the Times when the Sun is at a Certain Azimuth
Observing Changes in the Times and Azimuths of Moon Rise and Set Throughout a Month
Observing a Thin Crescent Moon
User Preferences
Printing and Saving Results
Popup Blockers
Script Timeout
Running the Sun/Moon Calculator as a Local Application
Determining Azimuths and Altitudes of Natural and Man-Made Features
Legal
Introduction
Main Form Layout
The Sun/Moon Calculator opens with the main form displayed, as shown in
Figure 1.
![[Image: Calculator Main Form]](images/MainForm.png "Click to enlarge image")
The main form is divided into several areas.
Location
You can set the location in one of several ways:
- Selecting a location from the calculator’s built-in database.
- Looking up a location in an external database, such as GeoNames Web Services. With the GeoNames database, the location properties are filled in automatically; with others, the properties must be entered manually.
- Specifying the locations properties; this may be the only choice for a location for which you have only the geographical coordinates, such as from a GPS reading.
Rise and Set Times
You can show Sun and Moon rise and set times for a specified range of dates. You can also specify criteria such as ranges of azimuth and altitude to find dates on which the Sun or Moon is in a given position, such as near a natural or man-made landmark; this capability is arguably the calculator’s most important feature.
You can show Sun and Moon positions at various times during day. The start and end times can be given directly, or they can be given relative to a Sun or Moon event such as rise or set.
Bottom-of-Form Buttons
Buttons at the bottom of the form let you display Sun and Moon rise and set times or positions, set the current date or reset all values to default, or run other applications that can help plan a shot.
- Display
- Shows the results of the calculations on the screen.
- Formats the results for printing, and in most cases, opens the browser’s Print dialog.
- Today
- Sets the current date for rise and set times and positions.
- Reset
- Resets all fields to their default values.
- Opens the Sun/Moon Search Criteria form. With some browsers, if the Use tabs for all pages preference is selected, and the Sun/Moon Search Criteria tab already exists, it may be necessary to manually select that tab.
- Az/Alt Tool
- Runs the Sun/Moon Calculator Az/Alt Tool, which you can use to find the azimuth, altitude, and distance from camera positions to natural or man-made features. This is a very simple tool compared to The Photographer’s Ephemeris, but it can be helpful if you need to include the heights of man-made features.
- TPE
- Runs The Photographer’s Ephemeris Web App, which shows Sun and Moon azimuths as lines on a map, and allows finding azimuth, altitude, and distance to natural features; if you don’t need to include the heights of man-made features, this is usually more useful than the Az/Alt Tool because it includes the information about the Sun and Moon.
Basic Operation
Using the calculator to get the basic information is simple: select or specify a location, select the type of calculation (rise and set times or Sun and Moon positions), select the desired date or dates (and the desired start and end times for positions), and click the Display or Print button.
Advanced Features
The calculator also has advanced features to accommodate special requirements. “Official” times of Sun and Moon rise and set are for a level horizon, as one would encounter on a seacoast. If the horizon consists of mountains rather than an ocean or a flat plain, the times when the Sun and Moon actually are visible can be quite different from the official times of rise and set. The Sun/Moon Calculator allows the rise and set to represent the times at which the Sun or Moon crosses a point at any angle above the horizontal plane. The calculator can find dates on which the Sun or Moon rises or sets in a particular direction, and again, rise and set are not limited to a level horizon. This feature can be helpful if you require that a landscape be illuminated from a specific direction, or want to have the Sun or Moon rising or setting near a natural or man-made feature.
Sun and Moon Coordinates
The positions of the Sun and Moon are given in terms of azimuth, the clockwise angle from north, and altitude, the angle above the horizon. These terms are explained in greater detail in the Glossary of the Sun/Moon Calculator Reference.True North or Magnetic North
The calculator can display Sun and Moon azimuths relative to either true north or magnetic north; the former often is preferable when working with a map, but the latter may be more convenient for comparison with field measurements made with a compass. The type of display is selected on the User Preferences form.
Context-Sensitive Help
The calculator provides context-sensitive help for most inputs and
output data—
Select a location from the database,
is displayed. Clicking on the label or output column heading brings up
the appropriate section of the Sun/Moon Calculator Reference.
User Preferences allow certain features
to be enabled or disabled, and allow control over how the calculator
displays information.
If you are near one of the locations in the built-in database, selecting
that location usually will suffice; differences of a few miles are
insignificant. Alternatively, you can browse the database by clicking
the List Locations button; when the cursor is
passed over a location name, the cursor changes to a hand pointer, and
the tooltip Set location to name is
displayed; clicking on the location name selects that location and gives
focus to the main form (if your browser is set to open pages in tabs,
you may need to manually select the tab for the main
form).
If Show Location search is enabled via User Preferences, you can search the
built-in database for a location that matches a pattern; if you know
that a location is in the database, this often is the fastest way to
select it. Enter the pattern in the text box after Search for; the search begins when the first
character is entered, and is updated as each additional character is
entered. A location matches if any part of its name contains the
pattern; pressing Enter or clicking Next Match finds the next matching location. This
can be convenient for rapidly scrolling through several locations that
match the same pattern; for example, entering TX
and pressing Enter several times finds all
locations in Texas. A message is given after the last matching
location; clicking New Search repeats the
search, beginning with the first match.
The search is case-sensitive if the pattern contains any
uppercase letter; you can reduce the chances of a matching an unwanted
location by observing capitalization. For example, enter AB to match locations in Alberta, Canada and avoid
matching Moab, UT. If you use any capital letters, you must use them
wherever they appear in a location name: either san
fran or San Fran will match San Francisco, CA,
but San fran will not.
All entries are stored as ASCII text, so the pattern should not contain
accented characters. To match Orléans, France, enter Orleans, F.
By default, the search pattern is ordinary text. If you are familiar
with Perl-style regular expressions, you can enable Allow regular expressions in location searches to
possibly save a few keystrokes when a long pattern is needed to match a
location. For example, NP.*UT allows a quick
search of all National Parks in Utah.
If your location is not near one of those in the built-in database, you
can usually look up the location properties using one of the online
service options in the Specify: area.
The latitude and longitude for many locations can be found from one of
the databases in the list following Look Up a
Location; select the desired database from the list and click Go.
If you enter a location name, a query using the GeoNames Web Services, the USGS XML Service, or the GNIS lookup service
provided by the USGS Texas Water Science
Center will automatically fill in the location’s properties,
usually including time zone and elevation, if a matching location is
found. Google
Maps or Bing
Maps can show a topographical map of the location, using either
the latitude and longitude or the name that you have entered.
The other databases provide only lookup, requiring you to transfer the
values to the Sun/Moon Calculator. The GeoNet Names
Server and
Getty Thesaurus give only latitude and longitude; the USGS
GNIS also gives elevation. timeanddate.com gives
latitude, longitude, time zone, and information about the observance of
daylight saving time.
In some cases, you may need to enter location properties in the fields
in the Specify: area.
The location Name is optional, but is used
to determine the rules for daylight saving time, so it is a good idea to
provide a name even if all you have for the location are GPS
coordinates. The format that the calculator understands is
place, country (for Canada and the United States, the
two-letter abbreviation for province or state (including the District of
Columbia, American Samoa, Puerto Rico, and the US Virgin Islands) is
used rather than the country (e.g., Washington, DC).
The Latitude and Longitude
may be entered as DMS (degrees:minutes:seconds), decimal degrees, or
combination thereof.
You can either select a Time Zone
from the list, or have it calculated from the longitude; if you know the
time zone, it’s usually better to select a value. Finally, select
Yes from the Uses Daylight
Time? box if the location observes daylight saving time, or No if it does not.
The angle and time input formats are described in detail in the section
DMS and HM Input in
the Sun/Moon Calculator Reference. Location lookup is described in the
section Look Up a
Location.
The selected location and any user-specified location are remembered
across sessions; this saves repeated entry if your normal location is
not in the database. Unfortunately, only one user-specified location is
saved. If your browser does not support Web Storage, cookies must be
enabled for these data to be saved.
This is the simplest and most obvious application.
On the calculator main form, ensure that the Rise and Set Times radio button is selected; select
the desired Start Date, set the End Date to the same date, and click the Display button. To print the results, click the Print button at the bottom of the results page.
If you are planning a trip, you may need the rise and set times for more
than one day.
On the calculator main form, ensure that the Rise and Set Times radio button is selected; select
the desired Start Date, then click the
appropriate radio button to specify either the desired End Date or a Date Offset, and
click the Display button. It’s often more
convenient to specify a date offset (e.g., two weeks) than a specific
end date.
If you plan to visit several locations, repeat the procedure for each
location. If you just want to print the results, it is faster and
easier to click the Print button at the bottom
of the main form rather than the Display button
and then the Print button on the results page.
The default settings giving positions between sunrise and sunset often
are what are needed.
On the calculator main form, ensure that the Sun and Moon Positions radio button is selected, and
select the desired calculation Date. Ensure that
the default values of 0 min,
before, and Sunrise for Start Time, 0 min, after, and Sunset for End Time, and a Time Interval of 30 minutes are
selected. Click the Display button; to print
the results, click the Print button at the
bottom of the results page.
If you want Sun and Moon positions for several successive days, the + 1 day button makes it easy to advance
the date. If you just want to print the results, it is faster and
easier to click the Print button at the bottom
of the main form rather than the Display button
and then the Print button at the bottom of the
results page.
If you plan to photograph a rising Moon, the default settings may not be
the most appropriate. For example, if moonrise is close to the time of
sunset, you may want to show positions at 5-minute intervals between
moonrise and 20 minutes after sunset. For Start
Time, enter 0, and select before and Moonrise; for End Time, enter 20, and select
after and Sunset. Select a
Time Interval of 5 minutes.
For a setting Moon near the time of sunrise, you might want to show
positions between 20 minutes before sunrise and zero minutes after
moonset. For Start Time, enter 20, and select before and Sunrise; for End Time, enter 0, and select after and Moonset. Select a Time Interval
of 5 minutes.
Alternatively, you can show positions between two specified times, or
between a Sun or Moon event and a specified time; with the default
values of 00:00 and 24:00
(or 12:00 am and 12:00 am),
clicking the radio button to the left of each time will show positions
from midnight until the following midnight. Times may be entered in
either 24-hour format or AM/PM format, using either decimal hours or
hh:mm format; see DMS and HM Input in the Sun/Moon
Calculator Reference for a more detailed description. A start time of
12:00 am is interpreted as midnight at the beginning of the date;
an end time of 12:00 am is interpreted as midnight at the end of
the date.
Some pairs of inputs are mutually exclusive; when one is selected, the
other is inactive. For example, when calculating Sun and Moon rise and
set times, if End Date is selected, Date Offset is deselected and inactive. Similarly,
when calculating Sun and Moon positions, if a time value is selected,
giving the start or end time relative to a Sun or Moon event is
deselected and inactive. By default, the inactive inputs are disabled;
this makes it more obvious which inputs are active in the calculation
but require that you click the appropriate radio button to reactivate a
disabled input or change its value; if Enable inactive
inputs in active area on User Preferences form is selected, you
can simply enter a value in the desired field without having to first
click the radio button.
For some items you select from a list of options; for others, you enter
a value. If you enter an invalid value (e.g., a Date
Interval of 0), the value will often be
changed to a reasonable valid value; you can either accept this value or
enter another valid value. In other cases, the field for which you have
entered an invalid value will be highlighted, and an error message will
be displayed below the field (with Firefox, you need to pass the cursor
over the highlighted field to display the message); the message will
explain why the value is invalid. If a particular field (e.g., Time Offset) requires values to be within a certain
range, that range will be indicated:
Please enter a valid value
With most browsers, you will need to correct the error before doing
anything else; with others, such as Firefox, you are not forced to
correct the error immediately but will be unable to perform a
calculation until you enter a valid value; when this happens on the Sun/Moon Search Criteria form, you will be unable to
save changes until the invalid entry is corrected.
In most cases, an entry that is blank or consists only of spaces will be
changed to the default value for that field; this provides an easy way
of resetting one field rather than the entire form.
By default, the Sun/Moon Calculator shows Sun and Moon rise and set
times that correspond to standard values: first appearance of the top of
a body above a level horizon. In some cases, this may not be what you
want.
For a location in a valley bounded on the east and west by mountains,
the Sun and Moon will appear above the eastern horizon later than the
official time of rise, and will disappear below the western horizon
earlier than the official times of set. In such situations, it’s
often more useful to know when the Sun and Moon cross the visible
horizons.
Sometimes you may want to find dates on which the Sun or Moon rises or
sets in a given direction or meets certain additional criteria, such as
rising or setting near a landmark, the Moon having a certain phase at
rise or set, the Moon rising or setting within a specified time of
sunrise or sunset, or the Moon rising or setting when the Sun is within
a certain range of altitudes.
You can do this by entering the desired criteria on the Sun/Moon Search Criteria form
and then calculating rise and set times to find dates on which those
criteria are met.
Standard times of Sun and Moon rise and set assume a level horizon
(i.e., zero altitude). This is fine if you are on a small, flat island
in the middle of an ocean, but less useful if you are in a valley
bounded by hills on the east and mountains on the west, and you want to
know when the Sun or Moon will be visible. Suppose, for example, that
the hills to the east have an altitude of 3° and the mountains
to the west have an altitude of 8°.
On the calculator main form,
ensure that the Rise and Set Times radio
button is selected, and click the Search Criteria... button to open the Sun/Moon Search Criteria form (with some
browsers, if the Use tabs for all pages User Preference is selected, and the
Sun/Moon Search Criteria tab already exists, it may be necessary to
manually select that tab).
Check the boxes at the left of the items in the Event column, and enter 3 in the
first text boxes in the Altitude column
for Sunrise and Moonrise,
and 8 in the first text boxes for Sunset and Moonset; the
checkboxes at the left of each row in the Altitude column will be automatically checked if they
are not already checked. Note that the values entered in the first text
boxes are automatically copied into the second text boxes when you click
anywhere outside the first text boxes. Leave the default values of Top selected so that the times indicate when the tops
of the Sun’s and Moon’s disks emerge from behind the hills
or disappear behind the mountains; when you are finished, the form
should appear as in Figure 2.
Click the Apply Settings button to apply
these values, and, if you wish, the Close button
to close the form. Calculate the rise and set times for the appropriate
dates.
In practice, it will seldom be quite this simple, because the altitude
of the horizon will usually vary with azimuth.
You may envision a photograph in which the early morning light
illuminates the scene from a particular direction, or perhaps you
envision a composition in which the Moon rises in a certain spot. For
example, suppose that you want to capture the light on a nearby mountain
peak at sunrise, and have determined that, because of intervening
mountains, the first light from the Sun strikes the peak only when the
Sun’s azimuth at rise is between 61° and 67°.
On the calculator main form, ensure that the Rise and Set Times radio button is selected, and click
the Search Criteria... button to open the
Sun/Moon Search Criteria form. If
you have done a previous search, either clear the values individually,
or click the Reset button to reset all values to
default and click OK when prompted to confirm.
In the row for Sunrise, check the box at the
left of the Event column, and enter the values
61 and 67 in the text boxes in
the Azimuth column. In the Altitude column, ensure that the box at the left is
unchecked or that the Top radio button is
selected; the form should appear as in Figure 3.
Click the Apply Settings button to apply
these values, and, if you wish, the Close button
to close the form. Ensure that the setting (True
North or Magnetic North) under Azimuth Display on the User Preferences form
matches how you obtained your azimuths. Select an appropriate range of
dates, and click the Display button on the main
form to find the dates on which the light you want is possible.
The best days for a landscape photograph with a full moon are often
those on which the Moon rises close to the time of sunset.
On the calculator main form, ensure that the Rise and Set Times radio button is selected, and click
the Search Criteria... button to open the
Sun/Moon Search Criteria form. If
you have done a previous search, click the Reset
button to reset all values to default and click OK when prompted to confirm.
In the row for Moonrise, check the box in the Event column, and check the box in the Moon–
Click the Apply Settings button to apply these values,
and click the Close button to close the form.
Select a location, and 1 January of the current
year and a date offset of 1 years to examine the
current year. Click the Display button to show
the dates.
The default values assume conventional rise and set for which the top of
the Moon crosses zero altitude, and assume that the Moon would be
photographed sometime after rise or before set at an altitude greater
than zero; they usually give a rough idea of good dates on which to
photograph the Moon during twilight.
If you specify a nonzero altitude or an altitude range for
Moon rise or set, you should also specify the time range for which you
want the Moon within the specified altitude range.
For example, in San Francisco, most east-facing locations have hills on
the horizon, and the Moon may not be visible until it reaches an
altitude between 1° and 2°. You might decide that you want to
photograph a full moon at an altitude between 2° and 5°, at a
time between 5 minutes after sunset and 25 minutes after
sunset. Giving these criteria for 2014 yields 11 dates, ranging from
January to December, with azimuths ranging from 72° to 118°.
Seldom does every potential date prove worthwhile, but results like
those above provide a good starting point. With such a list of dates,
you would then need to find suitable locations for each date and
determine whether one or more of them might provide a picture that you
wanted to take.
One method for finding locations is to find the Moon azimuth that
corresponds to the middle of the desired altitude range, and draw lines
on a map corresponding to that azimuth to see if the view from a
potential camera position affords an interesting composition. For the
last example, the mean altitude would be 3.5°; on 10 August
2014, the corresponding azimuth would be 106°. This occurs at
15 minutes after sunset; the pink sky color would largely be gone,
but building lights would be starting to come on, so a good view might
feature several prominent buildings.
Alternatively, you could require that moonrise occur while the setting
Sun is between −5° and −1°. Ensure that the Sun/Moon Search Criteria form has the default values. Check
the event boxes for sunset and moonrise, and enter -5 and -1 in the altitude column
for sunset; the button at the right of the column is automatically set
to “Ctr”. The form should appear as
in Figure 5.
Click the Apply Settings button to apply
these values, and proceed as with the previous example. You should get
similar—
There is a fascination of late with
“supermoons”—
To find rising “supermoons” near sunset, you could specify a
semidiameter range of 0.276° to the maximum of 0.284°, and
perhaps a Moon–
For San Francisco, a search of 2015 should give three results.
There is no standard definition of “supermoon”; the value to use in
a search for a photographic opportunity is largely a matter of personal
preference, presumably related to some compositional effect you are
trying to achieve. Obviously, the greater the minimum semidiameter, the
fewer the dates that will be found.
You may envision a photograph in which the Sun or Moon rises or sets
near a natural or man-made feature. The procedure for finding dates on
which this may happen is straightforward, but it does involve some
effort. Fortunately, much of the necessary information is readily
available from online resources.
Getting information about the location is the first step, and usually is
the one that requires the most effort.
If you use field measurements, and getting directions to other
features is too much trouble, having a photograph of the scene and
knowing the focal length (and hence the angle of view) of the lens
can serve much the same purpose.
If you use mapping software or geodetic calculations, a GPS reading
can assist in accurately fixing a camera position; with accurate
coordinates for a camera position, you can later determine
directions to any feature that you can locate on a map.
If the scene involves man-made features, find the heights of
those features from a source such as the
Skyscraper Page,
Emporis, or the
Skyscraper Center,
and add those heights to the base elevations when determining
altitudes.
Once you have the information about the location, decide where you want
the Sun or Moon to appear in the image:
Once you have the information for the location, and have an idea of
where you want the Sun or Moon, finding dates with the Sun/Moon
Calculator is straightforward:
In this example, you’ll consider a location with essentially a
single camera position, and specify criteria for azimuth and altitude at
moonrise to give alignment with a tall building.
A San Francisco location on Lincoln Avenue overlooking Crissy Field
affords a good view of the downtown skyline, or at least the top of
it—
The Skyscraper Page gives
the height of the Transamerica Building as 260 m (853 ft), and
the diagram indicates that the height to the base of the spire is about
200 m (656 ft). You assume a height of 5 ft at your
camera position.
With these values, you can use the Sun/Moon Calculator Az/Alt Tool to
determine the azimuth and altitudes to the Transamerica Building. With
the location set to San Francisco, CA,
click the Az/Alt Tool button at the bottom of
the main form; depending on the size of your browser window, the Az/Alt
Tool should look something like Figure 7
when it opens. To match this example, ensure that the units are set to
English.
Click on the red “To” marker (
Click the Fit button to show the big picture;
with a terrain map, the appearance should be as in Figure 9. It can be seen that the azimuth to
the Transamerica Building is 101.5° relative to true north, and that
the altitude to the top of the spire is about 2.2°. By entering 656 for the height of the Transamerica Building, it can
be shown that the altitude to the bottom of the spire is 1.6°.
The difference between the top and bottom of the spire is 0.6°,
slightly greater than the Moon’s mean angular diameter of
0.5°. You would like to capture the Moon approximately centered on
the spire, but you realize that if you insist on a perfect alignment,
you aren’t likely to find many dates. You still want exact
alignment in azimuth, but will accept the Moon with its center between
the base and top of the spire, in essence an altitude tolerance of
±0.3°. The resulting alignment criteria are shown in
Figure 10; the “window” of
azimuth and altitude is the vertical yellow line.
Click the Preferences link at the top of the
main form to open the User
Preferences form. To make examining individual dates easier,
select the option to send the Sun and Moon positions to a different
window than that for the rise and set times, so that the latter is not
overwritten by the position results; to do this, check the box in front
of Show rise/set times and positions in separate
windows. On the same form, ensure that the setting under Azimuth Display is set to True
North; save the settings using the Apply Settings button; close the form to avoid
the clutter of too many open windows.
Ensure that the Select: radio button is selected;
from the Select: drop-down box, select San Francisco, CA as the location. Alternatively,
enter san f in the text area after Search for; this should set the location to San
Francisco. If you prefer to search, be careful with capitalization, as
discussed under Searching the Database for a
Location.
On the calculator main form, ensure that the Rise and Set Times radio button is selected, and click
the Search Criteria... button to open the
Sun/Moon Search Criteria form. If
you have previously specified rise or set criteria, either clear the
values individually, or click the Reset button
to reset all values to default and click OK when
prompted to confirm.
In the row for Moonrise, check the box at the
left of the Event column; in the Altitude column, enter 1.6 in
first text box and 2.2 in the second text box.
Note that the Ctr radio button is automatically
selected when you click anywhere outside the second text box; this
happens whenever the two altitudes differ. In the Azimuth column, enter 101.5 in
the first and second text boxes; the filled-in form is shown in Figure 11.
Click the Apply Settings button to
apply these values; you may want to leave the form open in case you need
to refine your criteria.
Set the Start Date to 1 January
1990, click the Date Offset radio button,
enter 20, and select years.
Ensure that the Date Interval is 1 days. The form should appear as in
Figure 12.
Click the Display button on the main form to
find the dates that meet your criteria.
Depending on the computer and the browser, the calculation may require
anywhere from a few seconds to more than a minute. With their default
settings, some older browsers may give a warning about a script causing
the browser to run slowly, with a prompt asking if you want to abort
the script. If so, click No to allow the
calculations to continue; you may need to do so several times. See the
section Script Timeout for information
on how configure your browser so that you do not get this message. With
most current browsers, JavaScript performance is vastly improved, and
such warnings are now uncommon.
You get more than 40 dates, and are pleased by the many opportunities to
get your shot. Upon closer examination, however, you notice that on
most of the dates, the Moon is far from full, and in many cases moonrise
occurs during the middle of the day when it is uninteresting, or late at
night when it is far too dark to capture the foreground. You now
realize that you wanted the Moon close to full, but forgot to so
indicate. You would like some of the city lights to be on, but would
also settle for pink sky color without many lights; you decide that the
alignment should happen between 5 and 20 minutes after sunset. You
could specify a phase range, but your timing requirement will ensure
that the Moon is close to full, so that phase criteria are unnecessary;
moreover, if phase criteria were specified too narrowly, they actually
could exclude some dates that would be perfectly acceptable
aesthetically. The timing restriction is what you really consider
important, so that is what you decide to specify.
On the Sun/Moon Search Criteria form,
go to the Moon–
You see that the real possibilities are few and far between: you get two
dates: 13 August 1992 and 20 September 2002, as shown in
Figure 13.
You now want to examine each date to see how well it might match what
you had envisioned.
Pass the cursor over 13 Aug 1992; the cursor changes to a
hand pointer, and the tooltip
Set Sun and Moon Positions Date to 13 Aug 1992
is displayed. Click on the date to set the positions calculation Date to 13 Aug 1992. Return to
the main form; the Sun and Moon Positions radio
button should be automatically selected.
You decide that you want to see the Moon positions at one-minute
intervals between five minutes before and five minutes after the time at
which the Moon is near the top of the Transamerica Building. With the
Sun/Moon Calculator, “moonrise” is the time that the Moon
crosses the specified altitude; when an altitude range is specified, the
altitude crossing shown in the search results is the average of the
minimum and maximum values, in this case 1.9°.
You can specify your desired time range as follows: for the Start Time, enter 5 the text box
before min, and select before and Moonrise. For the End Time, enter 5 the text box
before min, and select after
and Moonrise.
Times entered in this manner will be automatically adjusted for
different times of moonrise, and you will not need to change them for the
different dates. Select a Time Interval of 1 minute; the form should appear as in Figure 14.
Click the Display button to show the Sun and Moon
positions; the results should be as in Figure 15.
Visually interpolating the azimuth to 101.5°, you note that when the
Moon is aligned with the Transamerica Building in azimuth, its altitude
is just over 1.7°, near the bottom of the spire. Although this
meets your criteria, you now recognize that it’s lower on the
building than you would prefer. Return to the times results window,
click on 20 Sep 2002, and on the main form,
click the Display button to show Sun and Moon
positions for 20 September 2002.
On this date, when the Moon’s azimuth is 101.5°, its altitude
is 2°, just above the middle of the spire; you decide that this is
just what you want. Further analysis will indicate that with the same
criteria, the only other matching dates between 1990 and 2090 are in
2026 and 2086.
A Sun altitude range may seem less familiar than a time range relative
to Sun rise or set, but it is generally a better indicator of sky
illumination, and it is less variable with latitude and season.
Rather than specifying a moonrise–
A Sun altitude range and a time difference are essentially two
different ways of imposing the same requirements, so specifying both
makes little sense, and accordingly it is not allowed; if you give both,
you will get an error message when you try to apply the settings.
For this example, you should get the same results with either approach,
but that will not always be the case. There isn’t a fixed
relationship between Sun altitude and the time relative to Sun rise or
set; rather, it varies with geographical latitude and the time of year.
For a given location and time of year, the Moon–Sun time
difference shown when you specify a Sun altitude range gives a rough
idea of the relationship. You can easily compare the two approaches by
checking and unchecking the appropriate boxes and repeating a search.
A similar search for alignment of a rising new moon with the
Transamerica spire could be done by giving a time difference relative to
sunrise, or by giving a sunrise altitude range. Because a new moon is
considerably less bright than a full moon, you might want to require a
slightly darker sky, either by increasing the time before sunrise or
decreasing the limiting Sun altitudes.
It makes no sense to give altitude ranges for both sunrise and sunset
with criteria for the Moon, and accordingly, doing so is disallowed.
Using a Sun altitude range is sometimes more complicated than using a
time difference, especially if the minimum or maximum Sun altitude is
close to the visible horizon. The calculator follows the convention of
correcting for atmospheric refraction when doing so makes the upper limb
visible, and not correcting otherwise. Because of this correction,
there is a step change in altitude when the Sun’s upper limb
crosses the visible horizon, and consequently, there is a range of Sun
altitudes that do not occur. If either limit for a Sun altitude range
is within this “forbidden” range, you will get an error
message to that effect; if this happens, specify a slightly different
value for the upper or lower altitude limit.
In this example, you’ll consider a location with essentially a
single camera position, but with far less restrictive alignment
criteria. You’ll also use the GeoNames Web Services to look up the
location.
The Movie Flat area of California’s Alabama Hills has many
locations that afford a good view of Mount Whitney and Lone Pine Peak,
often with interesting foregrounds. The lighting on the peaks at
sunrise can be spectacular, especially in winter months. You would like
to capture this, and also have the Moon somewhere in the general
vicinity. Accordingly, you decide on an approximate area in which you
want the Moon to appear in the image, and you want to find all dates in 2016
on which this might happen.
Using the Sun/Moon Calculator Az/Alt Tool or The Photographer’s
Ephemeris, you determine that the azimuths and altitudes to Lone Pine
Peak and Mount Whitney are approximately 247° and 13°, and
262° and 10.5°. You decide on an azimuth range of 243° to
263° and an altitude range of 10° to 16°, as shown in Figure 17. Not every position within this
range will give the desired result; in some cases, the Moon will be
behind one of the peaks. Accordingly, you will need to examine Moon
positions for every potential date to see if that date actually works.
The light on the peaks is most spectacular very close to sunrise, so you
also decide that you want this to happen between 2 minutes before
sunrise and 3 minutes after sunrise.
Movie Flat isn’t in the internal locations database, but you can
look it up using the GeoNames Web
Services. Click the Specify radio button, and
enter Movie Flat, CA; ensure that GeoNames Web Svc is selected in the box after Look up a location using:.
Click the Go button, and the properties for
Movie Flat should be automatically entered in the form. The indicated
location may not exactly coincide with your preferred camera position,
but it should be close enough for finding the appropriate dates.
On the calculator main form, ensure that the Rise and Set Times radio button is selected, and click
the Search Criteria... button to open the
Sun/Moon Search Criteria... form. If
you previously have specified rise or set criteria, either uncheck the
appropriate boxes in the Event column, or click
the Reset button to reset all values to default
and click OK when prompted to confirm.
In the row for Moonset, check the box at the left
of the Event column; in the Altitude column, enter 10 in the
first text box and 16 in the second text box; note
that the Ctr radio button is automatically
selected. In the Azimuth column, enter the 243 in the first text box and 263
in the second text box. The maximum azimuth value cannot be less than
the minimum; if you have previously entered a value less than 243°
for the maximum azimuth, that value is automatically changed to 243. If this happens, change the value for maximum
azimuth to 263.
Go to the Moon–
Click the Apply Settings button to apply
these values; click Close to close the form.
Ensure that Azimuth Display on the User Preferences form
is set to True North, and save this setting using
the Apply Settings button if necessary.
Set the Start Date to 1 January
2016, click the Date Offset radio button,
enter 1, and select years if
it is not already selected. Ensure that the Date
Interval is 1 days; the form should appear as
in Figure 19.
Click the Display button on the main form to
find the dates that meet these criteria; the results should be as
in Figure 20. For this example, the
calculator has been set to show whether the Moon is waxing or waning,
using an option on the User Preferences form
described in Miscellaneous Options. Here the
minus sign (“−”) appended to the phase indicates that
the Moon is waning in all cases. This is as expected; a general rule is
that a full moon sets at sunrise; for the Moon to be visible over
mountains, moonset must occur later than sunrise, and this usually
occurs several days after full moon.
You immediately notice that on some of the dates, the time relative to
sunrise is far outside of what you specified, and wonder what happened.
The results are a snapshot of Sun and Moon positions at the time at
which the Moon’s altitude is at the middle of the specified
range—
Pass the cursor over 23 Apr 2016; the cursor
changes to a hand pointer and the tooltip
Set Sun and Moon Positions Date to 23 Apr 2016
is displayed. Click on the date to set the positions calculation Date to 23 Apr 2016. Return to
the main form; the Sun and Moon Positions radio
button should be automatically selected.
Determine whether this is a valid date by showing Sun and Moon positions
between 11 minutes before sunrise and 8 minutes after sunrise.
For the Start Time, enter 11
in the text box before min, and select before and Sunrise. For the End Time, enter 8 in the text
box before min, and select after and Sunrise.
Select Time Interval of 1
minute, and click the Display to show Sun
and Moon positions for 23 April 2016; the results should be as
in Figure 21.
At 5:58 AM, 10 minutes before sunrise, the Moon is at 13° altitude
and indeed is outside the specified azimuth range, as shown in Figure 22. But at 6:06, 2 minutes before
sunrise, the Moon’s azimuth is just over 243°, within the
specified limits; the Moon is still within the specified limits at 6:11,
3 minutes after sunrise. The Moon is at the lower altitude of 10°
at 6:15, 7 minutes after sunrise. But the Moon’s path is
through the lower left corner of the specified ranges for azimuth and
altitude, so by the time it enters the specified window, it is behind
the shoulder of Lone Pine Peak.
For any date found by a search, the best approach is to examine Sun and
Moon positions and see if that date will afford a suitable image. The
simplest way to do this is to examine Moon positions between the
specified time limits—
On 17 September, the Moon passes behind Mount Whitney, and will be
about a diameter below the summit and slightly more than a diameter to
the right at 2 minutes before sunrise, as shown in Figure 23; because the Moon will be less
prominent in the overall scene, this might be a candidate for tight
framing with a long lens.
The Moon will be directly above Mount Whitney at about 6 minutes
before sunrise; at that time, you would probably need separate exposures
for the Moon and the mountain (and perhaps another for the foreground)
to handle the contrast.
Of the four dates found, two are solid candidates, one
(17 September) is marginal, and one (23 April) has the Moon
occluded by Lone Pine Peak by the time it is within the specified
ranges.
Moon paths relative to features can of course be adjusted by changing
camera positions; as long as you can find a suitable foreground, many
other dates may provide suitable compositions. Obviously, the greater
the distance to a feature, the greater the required change in position
to achieve a given shift in Moon path.
The times for which Moon positions are displayed can be limited to those
that meet the search criteria by selecting Apply
search criteria to positions on the User Preferences form. Do this and
return to the results page for matching dates.
Pass the cursor over 25 Mar 2016; the cursor
changes to a hand pointer and the tooltip
Set Sun and Moon Positions Date to 25 Mar 2016
is displayed. Click on the date to set the positions calculation Date to 25 Mar 2016. Return to
the main form; the Sun and Moon Positions radio
button should be automatically selected.
The start and end times should be 00:00
and 24:00, and the time interval should be set to
1 minute. Click the Display button to show Sun and Moon positions;
results should be as shown in Figure 24.
This is as expected; because the time requirement is the most
restrictive, the positions that meet the criteria are between 2 minutes
before sunrise and 3 minutes after sunrise.
Repeat the procedure for the other three matching dates. The results
for 23 April and 19 August should be as expected: 2 minutes
before sunrise to 3 minutes after sunrise.
But the result for 17 September indicates no matching times:
A general rule is that a full moon rises and sets opposite the Sun;
consequently, the lighting on a feature in the Moon’s direction is
often flat. When the Moon sets significantly later than the Sun, as is
always the case for a nearly full moon over mountains, the lighting is
more directional, providing some modelling of the mountain features. In
some cases, the directionality of the lighting can be a criterion for
choosing among potential dates.
The lighting directionality can be seen by comparing the azimuth of the
rising Sun with that of the Moon at the time of altitude crossing. For
example, on 25 February, the light from the Sun comes from about
25° to the south of the direction to the Moon, roughly the same as
for the image used in Figures 14–
In this example, you’ll consider a location with an essentially
unlimited number of camera positions, and use the GeoNames Web Services to look up the
location.
You want to capture the Moon setting near California’s Mount
Williamson from Manzanar, and you want to find all the
dates between 2010 and 2040 on which this might happen.
In many locations, potential camera positions are quite limited; this
isn’t the case near Manzanar, which affords an almost continuous
range of positions easily accessible from the Manzanar cemetery road,
with azimuths to Mount Williamson ranging from about 237° to 243°
relative to true north. The altitudes from those locations range from
about 11.6° to 11.9°; the sections Mapping Software and Geodetic Calculations describe methods
for determining those values. Searching for dates for each possible
location would be an almost endless task, so you decide to allow for the
full range of azimuths and altitudes, and then examine each of the
matching dates to see if they work for one or more specific locations.
You decide that you nominally want the top of the peak between the
center and bottom of the Moon, and want the center of the Moon to be
within two diameters (1°) on either side of the peak. With the
center of the Moon at the top of the peak from the location with the
lowest altitude to the peak, the altitude of the Moon’s center is
11.6°; with the bottom of the Moon at the top of the peak from the
location with the greatest altitude, the altitude of the Moon’s
center is approximately
11.9° + 0.25° = 12.15°.
With your tolerance of the Moon being
within ±1° of the center of the peak, the azimuth range is
236° to 244°. To ensure that you don’t miss any dates,
it’s usually better to specify a slightly wider range than you
think you need—
You also want the first sunlight on Mount Williamson, and accordingly
want the Moon to be near the top of Mount Williamson between two minutes
before and three minutes after sunrise. You could specify a phase
range, but, as with the previous example, your timing requirement will
ensure that the Moon is close to full, so that phase criteria are
unnecessary. Once again, the timing restriction is what you really
consider important, so that is what you decide to specify.
Manzanar isn’t in the internal locations database, but you can
look it up using the USGS GNIS XML
Service. Click the Specify radio button, and
enter Manzanar in the Name:
box; ensure that USGS GNIS XML Service is selected
in the box after Look up a location using:.
Click the Go button; there should be only one
matching location, so the properties for Manzanar should be
automatically entered in the form. The indicated location may not
exactly coincide with the Manzanar National Historical Site, but it
should be close enough for finding the appropriate dates.
On the calculator main form, ensure that the Rise and Set Times radio button is selected, and
click the Search Criteria... button to
open the Sun/Moon Search Criteria form.
If you previously have specified rise or set criteria, clear the values
individually, uncheck the appropriate boxes in the Event column, or click the Reset button to reset all values to default, and
click OK when prompted to confirm.
In the row for Moonset, check the box at the left
of the Event column; in the Altitude column, enter 11.5 in
the first text box and 12.2 in the second text box;
note that the Ctr radio button is automatically
selected. In the Azimuth column, enter the 235 in the first text box and 245
in the second text box. The maximum azimuth value cannot be less than
the minimum; if you have previously entered a value less than 235°
for the maximum azimuth, that value is automatically changed to 235. If this happens, change the value for maximum
azimuth to 245.
Go to the Moon–
Click the Apply Settings button to
apply these values; you may want to leave the form open in case you need
to refine your criteria.
Ensure that Azimuth Display on the User Preferences form
is set to True North, and save this setting using
the Apply Settings button if necessary.
Set the Start Date to 1 January
2010, click the Date Offset radio button,
enter 30, and select years.
Ensure that the Date Interval is 1 days; the form should appear as in Figure 27.
Click the Display button on the main form to
find the dates that meet your criteria.
You should get 15 dates, ranging from 2013 to 2039. You now want to
examine some of the dates to see if they might work from one of your
favorite locations.
Pass the cursor over 5 May 2015; the cursor
changes to a hand pointer and the tooltip
Set Sun and Moon Positions Date to 5 May 2015
is displayed. Click on the date to set the positions calculation Date to 5 May 2015 and return
to the main form.
In accordance with the search criteria, you decide that you want to see
the Moon positions at one-minute intervals between two minutes before
and three minutes after sunrise.
For the Start Time, enter 2
in the text box before min, and select before and Sunrise. For the End Time, enter 3 in the text
box before min, and select after and Sunrise.
Select Time Interval of 1
minute, and click the Display to show Sun
and Moon positions for 5 May 2015. Return
to the times results window and repeat the process for the other dates.
For each date, the task then reduces to finding suitable foregrounds
within the range of potential locations. Often, for a shot of this
type, a useful starting point is to have the Moon’s azimuth at
sunrise match that of the target feature, adjusting the distance until
the altitude to the feature results in the desired vertical alignment.
At sunrise on 5 May 2015, the Moon’s
azimuth is 237.71°, its altitude is 12.22°, and its semidiameter
is 0.256°. The altitude criterion was to have the top of Mount
Williamson between the center and bottom of the Moon; on 5 May 2015, this is equivalent to having the
altitude of Mount Williamson between 12.22° and 11.96°. To
accomplish this with the Moon aligned in azimuth with the peak, find a
direction for which the azimuth to Mount Williamson is 237.7°, and
find the range of distances for which the altitude criterion is met.
The task of finding a location is usually much easier if you use mapping software to find the azimuth and
altitude to the desired feature; in many cases, this can be accomplished
in few minutes.
Let’s try this for 5 May 2015, using The Photographer’s Ephemeris.
With the calculator’s location set to Manzanar,
CA, click the TPE button at the bottom of
the form; depending on the size of your browser window, you should get
something like Figure 28. TPE remembers
the type of map you last used; if you used satellite imagery,
you’ll see that rather than a terrain map. Initial positioning,
especially for natural features, is usually easier with a terrain map;
in this case, you’ll be relying on the clearly marked location of
Mount Williamson, so the type of map is less important. If you do
switch to a terrain map by clicking the Map control
in the upper right of the map, ensure that the Terrain box is checked.
Set the time to sunrise by pressing ‘,’ or
‘<’ until the white box near the bottom of the
map indicates Sunrise. The box should show the
Moon’s azimuth and altitude as 237.6° and +12.3°.
GeoNames seems to have a slightly different impression of
Manzanar’s location than that of the Manzanar NHS; click and drag
the red primary marker until it’s just west of the Manzanar
marking at the left of the map; you’ll refine the location later.
Click and drag the gray secondary marker along the blue-gray line
corresponding the Moon’s azimuth at sunrise; the map will scroll
as you near the edge. Continue dragging until you approach the marking
for Mount Williamson, and position the gray marker on that location.
Zoom in to ensure accurate placement; if necessary, change to satellite
imagery and zoom in even further.
Now center the map on the red primary marker by pressing
Shift-C or shift-clicking the primary-marker centering icon
near the upper right corner of the map; you then may want to zoom out
slightly. A map using satellite imagery is usually more useful when
fine tuning a camera position, so if you have a terrain map, switch to
satellite imagery using the control at the upper right of the map.
Click the red primary marker and drag until you find a
location that meets your initial requirements; to have the bottom of the
Moon at the top of the peak at sunrise, that location has azimuth and
altitude to Mount Williamson of about 237.7° and 11.59°.
The locations in this direction meeting the alignment criteria offer an
unobstructed view of Mount Williamson; the location aligning the peak
with the bottom of the Moon is next to a road, while the location
aligning the peak with the center of the Moon requires about a
quarter-mile hike. Figure 29 shows the
first location; the Manzanar cemetery is near the right of the map. It
can be seen that the gray line to Mount Williamson is nearly coincident
with the blue-gray line to the Moon.
Nominally, a full moon sets opposite a rising Sun, and the lighting on a
feature in the direction of the Moon is often flat.
It can be seen here that the line to Mount Williamson is not coincident
with the light orange line to sunrise; the light from the Sun comes from
approximately 11° to the south, so the lighting may provide some
modelling of the mountain. The lighting direction may be easier to
visualize by holding down the Shift key, which extends the
line to the Moon to the east; this is shown in
Figure 30.
The original azimuth criterion required alignment within ±1°;
you can adjust the azimuth to Mount Williamson by that amount to find
additional camera positions. The timing criterion allowed the alignment
to occur between two minutes before sunrise and three minutes after
sunrise; in this case, this allows additional azimuth variation of
−0.34°, +0.5°. During this period, the Moon’s
altitude ranges from 12.55° to 11.73°, so distances must be
adjusted accordingly to maintain alignment in altitude.
In this example, most camera positions offer essentially the same
foreground, which is fairly nondescript. Upon visiting the location,
you may find some interesting boulders to serve as foreground, á
la Ansel Adams, but the best choice may be to find a location
that’s easily accessible, and choose a fairly long lens for tight
framing of the Moon and Mount Williamson. Of course, if you want the
Moon to appear large in the image, you’ll need a long lens anyway;
with tight cropping, the immediate foreground becomes less important,
giving greater flexibility in the choice of camera position.
If you are willing to explore slightly less well maintained roads and
hike short distances, many additional camera locations near Manzanar are
available, including the location of Ansel Adams’s famous image of
Mount Williamson. With suitable adjustments to criteria to cover the
additional locations, a search of the same ranges of dates can yield a
considerable number of dates.
If you perform a search with overly restrictive criteria, you may get
the message
**** No dates meet criteria ****
To find some matching dates, you will need to increase the date range of
your search or compromise and relax your criteria, by expanding the
moonset altitude range, the moonset azimuth range, the moonset time
range, or combination thereof. You also may find that a slightly
different location (with a different azimuth and altitude to the peak)
will give better results. Continue the process until you find a
suitable date or until your criteria are so compromised that you no
longer want to capture the image, and decide to fake it with Photoshop.
By default, search criteria are only applied when showing Sun and Moon
rise and set times. But they can also be applied when showing Sun and
Moon positions by selecting Apply search
criteria to positions on the User Preferences form.
As with a date search, a position search is limited to either the time
between lower and upper transit (“rise”) or the time between
upper and lower transit (“set”). If the desired position(s)
span a transit, two separate searches are required.
Because of this, it is not possible to specify an altitude range for
both rise and set of a body. Specifying azimuth ranges for both rise
and set is allowed but will usually find nothing and accordingly is
inadvisable.
A single value for altitude is taken as the time at which the body
crosses that altitude, i.e., “rise” or “set,”
and not a search criterion; to specify a search criterion, give an
altitude range. All other criteria should be ranges, because an exact
match to a single value is unlikely. Unless a range of values is quite
broad, it’s usually best to set a calculation interval of 1 minute. Because of the way rise and set are
implemented, it’s usually also best to specify start and end times
of 0 hours and 24 hours local time.
A position search can be useful for quickly showing the times
on a given date when the search criteria for rise and set times are met,
especially if it is not obvious what to specify for start and end times.
It can also be used to confirm that a date found is valid; the date
search employs some approximations, and can occasionally show a date for
which the criteria are not met (although the difference will usually be
very slight).
Examining individual times is arguably a more foolproof approach, but it
isn’t perfect, and can miss times for which the criteria are met
only very briefly. Moreover, it is “brute force,” and is
noticeably slower is slower when searching a wide range of dates.
Because position display is limited to 48 hours, speed is less of an
issue, but because of this limitation, a position search cannot usually
be used as a substitute for a date search.
Using a position search on a result of a date search is easily done:
find the date(s) by calculating rise and set times, and then on the
results page, click on a date; this will select Sun
and Moon Positions on the calculator main form, set the date to
date, and set the start time, end time, and time interval to
appropriate values. If you prefer different values, you can set them
manually.
A position search can also be useful when a date has been chosen and the
objective is simply to find when the Sun or Moon will be at a certain
altitude or at a certain azimuth without requiring a narrow range of
both. Although it’s usually feasible to visually scan data for a
day to find the desired positions, it is arguably unnecessarily tedious.
Suppose you are in Sines, Portugal and want the times on 10 May
2023 at which the Sun’s altitude is between 45° and 46°.
With Look up a location using:, set the location
to Sines Municipality (you may get two results;
either will work in this case).
On the calculator main form, ensure that the Sun and Moon Positions radio button is selected, and click
the Search Criteria... button to open the
Sun/Moon Search Criteria form. If
you have previously specified rise or set criteria, either clear the
values individually, or click the Reset button
to reset all values to default and click OK when
prompted to confirm.
In the row for Sunrise, check the box at the
left of the Event column; in the Altitude column, enter 45 in
first text box and 46 in the second text box.
Note that the Ctr radio button is automatically
selected when you click anywhere outside the second text box; this
happens whenever the two altitudes differ. In the
Azimuth column, leave the box unchecked.
The filled-in form is shown in Figure 31.
Click the Apply Settings button to
apply these values; you may want to leave the form open in case you need
to refine your criteria. Results should be as follows:
A similar search could be done to find the times at which the Sun is
with a certain azimuth range. To do this in place of the previous
search, uncheck the box in the Altitude column
(there is no need to clear the values), check the box in the Azimuth column and enter the values 103 and 105. The filled-in form
is shown in Figure 33.
Click the Apply Settings button to apply
these values; results should be as follows:
In most cases, true north is the best choice when performing a search,
even if that means converting compass measurements. Magnetic
declinations change over time, so that as measured with a compass,
natural and man-made features appear to move.
Azimuths you specify as search criteria are static, however, so that
the azimuth range appropriate for the end of a search may be slightly
different from the range appropriate for the beginning. Using true
north usually is much simpler than having to figure out how to adjust
search criteria for changing magnetic declinations.
The Earth makes one orbit of the Sun in a year. The Sun’s rise
and set azimuths, as well as the day length and maximum altitude, vary
throughout the year. Observing the values for each throughout the year
may help in planning photographs of different locations. Select 21
December of the desired year as the Start Date, and select a Date Offset
of 1 year. Select a Date Interval of 1 month (or 1 week if you want
finer resolution). and click the Display button.
There are several measures of the Moon’s orbit; perhaps the most
familiar is the synodic month, in which the Moon returns to
the same position with respect to the Sun (and hence the same phase)
approximately every 29.53 days. The Moon returns to the same position
with respect to the fixed stars in the course of sidereal
month, which on average, is approximately 27.32 days. In the
course of a sidereal month, the Moon goes through its range of minimum
and maximum rise and set azimuths, as well as its least and greatest
maximum altitudes.
Using the default location of San Francisco, CA, click the Rise and Set Times radio button, set the
date to 21 December, and set a date offset of 30 days. Observe that the
approximate rise and set azimuths, and least and greatest maximum
altitudes repeat roughly every 27 days. Note that the full moon rises
and sets approximately opposite the Sun, both in time and azimuth (more
precisely, the Moon’s rise and set azimuths are approximately at
minimum and maximum when the Sun’s are at maximum and minimum).
Note also that full moon occurs close to the day of greatest maximum
altitude (it “rides high”).
Set the date to 21 June and repeat the calculations. Observe that,
again, the Moon rises and sets approximately opposite the Sun. Note,
however, that now the full moon occurs close to the day of least maximum
altitude (it “runs low”), the opposite of what happens in
Winter. This behavior is important if you plan to photograph
“moonbows” or make other photographs by the light of the
full moon.
Even these two examples do not illustrate the full range of the
Moon’s behavior. Because its orbit is inclined to that of the
Sun, its declination
varies between approximately ±18.1° and ±28.9°
over an 18.6-year period. The Moon’s phases and dates repeat
approximately every 19 years (the Metonic cycle), but the
repetition of the Moon’s position in a scene almost never is
exactly the same. Stated otherwise: there are few second opportunities
for scenes that include the Moon.
For millennia, many cultures have used the sighting of a new crescent
moon as the basis for their calendars. Although many modern lunar
calendars are calculated, some still rely on first sighting of a new
crescent moon to declare the start of a new month.
For many individuals, observation of a thin crescent moon may serve as
its own end.
Nominally, a new moon rises and sets with the Sun; a thin crescent
occurs in the morning on the days before a new moon and in the evening
on the days after a new moon. Although beginnings of calendar months
are usually done by sighting a new crescent moon in the evening, for
simple observations or photography, an old crescent moon rising just
before sunrise may be equally appealing.
Thin lunar crescent visibility is not shown by default; this can be
changed on the User Preferences form,
under Show thin lunar crescent visibility:. You
can show this information for morning observations, evening
observations, or both by checking the appropriate boxes.
The Sun/Moon Calculator considers a “thin” crescent moon to
be one with a phase of 0.15 or less; when the phase is greater, no
results are shown.
For example, to show morning and evening thin crescent moons in
Lynchburg, Tennessee for April 2019, check the boxes for both Morning and Evening under
Show thin lunar crescent visibility:
on the User Preferences form and save the
changes. Set the location, select Rise and Set
Times, and set the start and end dates. Click
Display; the result should be
The Time is the best time to make the observation,
calculated as 4⁄9 of the time between sunset and moonset (or
5⁄9 of the time between moonrise and sunrise).
A visibility Code of “A” predicts a
crescent that is easily seen and a code of “B” predicts one
that can be seen only under perfect conditions; other codes predict that
the crescent cannot be seen with the naked eye. The codes are explained
in detail under Code in the Sun/Moon Calculator
reference.
As can be seen, a thin crescent moon can only be observed on a few days
each month; examining a longer period of time would show a greater
number of opportunities. But unfiltered results for an extended period
would consist mainly of clutter.
The clutter could be reduced by giving Search Criteria.
A crescent moon with a phase of 0.15 isn’t really very thin, so
you might wish to specify a lesser upper limit; moreover, if the phase
isn’t great enough, the crescent will not be visible, so you might
also wish to specify a lower limit greater than zero.
The Sun/Moon Calculator applies all Search Criteria simultaneously;
because a morning thin crescent doesn’t occur on the same days as
an evening thin crescent, it isn’t possible to cover both in the
same search.
Let’s look at finding evening thin crescents. Begin by unchecking
the Morning button on the User Preferences form.
Then limit the moonset phase to the range 0.01–0.02 and check the
Waxing box (a waning crescent moon usually sets
before sunset, so it isn’t visible).
It may be helpful to show the time difference between sunset and
moonset; do this by checking the Moon–Sun Time
Difference box. By default, the moonset–sunrise time is
shown; to change this to moonset–sunset, select the Sunset radio button. A thin crescent isn’t
visible if the Moon sets before sunset; to avoid missing opportunities,
specify a fairly wide time range, e.g., 240 minutes, after sunset.
With these settings, a search for 2019–2020 should yield
A thin crescent moon can be difficult to locate, so it’s essential
to know where to look. The calculator can easily be set to show the
Moon position at the planned time of observation by passing the cursor
over the Time on the desired date and clicking.
For example, for an observation on 5 May 2019, pass the cursor
over the Time for that date; the cursor should
change to a hand pointer and display the tooltip
Set Sun and Moon Positions Time to 19:58 on 5 May 2019
Click on the date and return to the main form; the calculator should be
set to Sun and Moon Positions, with this time and
date set. Click Display to get
The visibility Code of “B” suggests
that the crescent would be visible only under perfect conditions;
however, the value of 0.166 for the parameter q is in the
upper part of the “B” range, so this could be a reasonable
opportunity to observe a very thin crescent.
If your location is substantially higher than the local horizon, enter
your height above the local horizon. This value is the difference
between your elevation and that of the local horizon rather than your
elevation above sea level. For example, if you are at an elevation
6000 ft and the elevation at the horizon is
4500 ft, the value to enter is 1500.
You also should enter a value if you want to know the time at which
first light will strike a nearby mountain; the value to enter is the
difference between the elevation of the mountain and the elevation at
the horizon. For example, if the horizon is at an elevation of 4000 ft, and you want to know when sunlight will
first appear on a 12,000-ft mountain, enter 8000.
The elevation at the horizon is not always easy to determine; see Height above
Horizon in the Sun/Moon Calculator Reference for additional
discussion.
The setting of this option is retained across sessions. If your browser
does not support Web Storage, cookies must be enabled for these data to
be saved.
The User Preferences form,
accessed via the Preferences link, allows you
to set several options that enable or disable certain features or affect
how the Sun/Moon Calculator displays information. A few of the options
are briefly described below; the other options are explained in the Sun/Moon Calculator Reference.
By default, results of times and positions calculations are sent to the
same window, with each new result overwriting the previous one. If you
don’t close the results window, it usually is possible to view
previous results using the browser’s history. However, it usually
is easier to select the Show rise/set times and
positions in separate windows option to send times and positions
calculations to separate windows This can be handy if you are searching
for dates that meet specified search criteria and you plan to
calculate Sun and Moon positions for several of the matching dates. You
save the trouble of having to remember the list of matching dates, and
you can save time by simply clicking on a matching date in the times
results to set the positions calculation Date to
that date.
Many browsers that support tabs can be set to allow the browser to
choose whether to open pages in new windows or new tabs. With a browser
so configured, by default, the search criteria and User Preferences
dialogs open in popup windows, and positions or rise/set times and help
open in new tabs. The Use tabs for all pages
option usually causes all pages, including dialogs, to open in new tabs.
If you are doing a search that may require several adjustments to the
search criteria, it may be easier to have this dialog in a tab rather
than a popup window. This option should also be selected if the browser
is set to open all pages in new tabs.
If either of these preferences is changed, any existing tabs or windows
for results, Help, or Tutorial pages should be closed to avoid
unexpected behavior.
The Show location search feature allows searching
the built-in database for a location that matches a specified pattern
rather than selecting from the list. In many cases, this may be faster.
For example, entering yellowst and clicking New Search (or pressing Enter)
provides a fast way to select Yellowstone National Park. If the pattern
contains any capital letter, the search is case sensitive; otherwise
case is ignored.
If you are familiar with Perl-style regular expressions and want to use
them in patterns, select Allow regular expressions in
location searches.
Show location search is enabled by default.
Select AM/PM if you want the time displayed in
AM/PM format (e.g., 12:25 am, 7:21 pm). Use the default
selection of 24 hour if you want the time
displayed in 24-hour format (e.g., 0:25, 19:21). Select Universal time (UT) if you want to show universal
time; in most cases, you probably want local time. Universal time is
incompatible with daylight saving time, and selecting UT will deselect
daylight saving time.
Select Show daylight saving time if you want
to show daylight saving time when it is in effect; deselect this option
if you wish to show standard time throughout the year.
If you will using a compass to measure azimuths in the field, you may
wish to select Magnetic North so that you don’t
need to add or subtract the magnetic declination for comparison. If you
will be comparing the results with directions on a map, use the default
selection of True North.
Choose either feet or meters for the input and display of the
location’s elevation and the height above the horizon.
Sometimes you may wish to know whether the Moon is waxing or waning.
The Sun/Moon Calculator indicates this by appending a plus sign
(“+”) or minus sign (“−”) to the phase
when showing rise and set times; a plus indicates a waxing Moon, and a
minus indicates a waning Moon.
This isn’t shown by default; you can force it to be shown
by checking one of the Moon Phase boxes on the
Sun/Moon Search Criteria form; you can keep the default
range of 0 to 1. That setting will not be maintained across sessions;
if you want this indication as a permanent feature, check the box next
to Always show whether Moon is waxing or waning
on this form.
If you work with both maps and compass measurements, you often need to
convert one type of value to the other unless your compass has a
built-in declination adjustment. If you have trouble remembering
whether to add or subtract the magnetic declination, checking the Show conversions between True and Magnetic North
option will indicate the required conversion on the results page. You
can, of course, calculate results using True North and again using
Magnetic North, and print both, but you then continually need to ensure
that you are referring to the correct printout.
The Use a font size of nn pt for printed
output option, explained in the next section, allows you to specify
a font size for printed output. With some older browsers, doing so may
be necessary to get acceptable printed output.
Although it is improving, printed output from most web browsers leaves
much to be desired, especially when printing wide tables.
Unfortunately, the behavior varies considerably among browsers.
Most current browsers do a reasonable job of shrinking the output to fit
on a page, and Firefox even repeats table headings at the tops of new
pages. With Firefox and similar browsers, best results are usually
obtained by checking a “Shrink to Fit” box (or similar) on
the browser’s Page Setup dialog and not specifying a font size for
printing. In some cases, it may be necessary to manually select a scale
rather than relying on automatic shrinking to fit.
With some older browsers, such as Internet Explorer 6, shrinking to fit
is less effective, and better results usually are obtained by specifying
a font size, typically 9–10 point for printing in portrait
orientation. If search criteria restricting the time difference
between sunrise or sunset and moonrise or moonset have been specified,
the output includes an extra column, so the smaller font size may be
needed; the default margins also may need adjustment. Some
experimentation using the browser’s Print Preview may be needed to
determine the best settings.
To specify a font size, click the Preferences
link to open the User Preferences form, check
the box in front of Use a font size of nn pt
for printed output, enter the desired font size, and click Apply Settings to save the values.
With most current browsers, saving with the browser’s
“Save” or “Save As” command will save the main
form rather than the results. To save the results as an HTML file, use
the “Save” button at the bottom of the results page. With
Microsoft Edge, Internet Explorer 11, and Vivaldi, the “Save
as” dialog may appear on the window or tab for the Sun/Moon
Calculator main form; with IE and Vivaldi, there may be no indication
(e.g., flashing tab, bold text in that tab) that a prompt is pending.
If the system has a PDF printer available, the results can be saved as a
PDF file by printing to that printer. The Adobe Acrobat browser Add-on
usually saves the main form.
Astronomical calculations are very computationally intensive; a search
extending over several years, such as those described in the examples in
the Advanced Calculations section,
requires the execution of millions of instructions, and is not really a
task for which a scripting language such as JavaScript was intended.
But improvements in JavaScript performance in recent years have been
nothing short of phenomenal, so the calculation times—
A script on this page is causing [your browser name] to run slowly. If
it continues to run, your computer may become unresponsive. Do you want
to abort the script?
If you get this message, click No to allow the
script to continue to run; unfortunately, you may need to do this
several times. If you conduct many searches, you probably will want to
change the default settings so that you no longer get the message.
Information about how to do this for Internet Explorer is given in the
Microsoft Knowledge Base article ID 175500, and
similar information about how to change the settings for Firefox is
available in
this article on John Walker’s Fourmilab web site. Be aware,
of course, that if you change your browser’s default settings, you
become more vulnerable to a truly runaway script.
Computers running Windows XP cannot run versions of Internet Explorer
later than version 8. IE 8 is far slower than any other major web
browser; accordingly, it is not recommended for date searches that span
more than a few years. As of June 2019, Microsoft Edge (version 42) is
by far the slowest of the major browsers; IE 11 has performance
comparable to most others.
All necessary files are included in a single
zipped file; download it and extract the files to a single
directory. To run the calculator, open the file SunMoonCalc.htm.
Because of security considerations, most browsers—
With Chrome, Firefox, or Opera, you must enable access to local files--see
"Running the Sun/Moon Calculator as a Local Application" in the
Tutorial.
With Chrome, this can usually be accomplished by giving the
where Chrome PATH is the folder path to Google Chrome and
SunMoonCalc PATH is the folder path to the Sun/Moon Calculator
(the actual shortcut must be on a single line).
A similar approach can be used with Opera, giving the same switch as
with Chrome.
With Firefox, you can change a setting with the Configuration Editor
by entering
Be aware that overriding the browser’s security features
may leave you vulnerable to certain malicious apps. If you
choose to do this, be very careful about internet browsing, and when you
are done using the Sun/Moon Calculator, restart the browser in normal
mode; with Firefox, restore the setting changed via
With Internet Explorer, you may get a message like
Internet Explorer restricted this webpage from running scripts or ActiveX controls.
You can then click Allow blocked content to continue.
For a more detailed discussion of running web applications locally, see
this
article. Although there sometimes are several ways to have browsers access
local files, the safest approach with Chrome or Opera is to create a
dedicated shortcut for the Sun/Moon Calculator, leaving security
restrictions in place otherwise.
Relating the coordinates given by the Sun/Moon Calculator to features in
an outdoor scene requires at least a rough idea of the coordinates of
one or more features.
Azimuths usually are measured with a compass, and altitudes usually are
measured with a clinometer. Surveyors use more sophisticated
instruments, but the cost, bulk, and complexity of those instruments
usually makes them impractical for photographers. Because the magnetic
and geographic poles do not coincide, a compass needle generally does
not point to true north. The difference between true north
and magnetic north is the magnetic declination. Some
compasses include a provision to adjust for the magnetic declination so
that they can indicate relative to true north; others do not, and
require that measurements made with them be converted to true north.
The Sun/Moon Calculator includes the option of showing azimuths relative
to magnetic north so that no conversion is needed. Better compasses
allow the user to sight the target while observing the pointer and
scale, usually giving greater accuracy.
It’s important to recognize the accuracy limitations of
measurements with compasses and clinometers. Under the best conditions,
it usually is difficult to measure altitude to better than
±½°, and azimuths often cannot be measured closer than
±1°.
There also are limitations in the World Magnetic Model (WMM) used to
calculate magnetic declinations. The portions of the geomagnetic field
generated by the Earth’s crust and upper mantle, and by electric
currents in the upper atmosphere and near-Earth space are essentially
ignored. Accuracy is typically better than ½°, but a compass
may sometimes exhibit anomalies of several degrees when compared with
the WMM. If ferromagnetic items are nearby (which is possible at almost
any urban location), errors in measured azimuths can be even greater.
For comparison, recall that the angular diameters of the Sun and Moon
are approximately ½°. Errors in the WMM are of course
in addition to any measurement errors.
Accordingly, calculated values of magnetic declination should be used
with caution, especially when planning precise alignments of the Sun or
Moon with natural or man-made features. If the positions of the camera
and the feature(s) of interest are accurately known, better estimates of
direction(s) from the camera to the feature(s) are often obtained from
mapping software or geodetic calculations.
Topographic mapping software from several suppliers includes the
capability of determining azimuths, often relative to either true north
or magnetic north. If your position and the positions of the features
of interest are accurately known, and your location is not extremely
close to those features, the azimuths determined by the software usually
are more accurate than those determined by compass measurement. At very
small distances between camera positions and features, slight errors in
positions result in considerable errors in azimuths; if the camera
position is not easy to pinpoint on a map, GPS coordinates transferred
to the software can improve accuracy.
The Sun/Moon Calculator Az/Alt Tool uses
Google™ Maps to determine the azimuth and altitude from
one location to another, and it can generate an elevation profile of the
terrain between the two locations, including a sight line to help
determine visibility of one location from the other. It allows you to
specify the additional heights of man-made structures. You can run the
Az/Alt Tool by clicking the Az/Alt Tool button
at the bottom of the main form; the map will be centered on the
location currently selected or specified in the Location area.
The Photographer’s
Ephemeris Web App also uses Google Maps to determine the azimuth and
altitude from one natural feature to another; it does not have provision
to specify the height of a man-made structure above the base elevation.
You can run the TPE Web App by clicking the TPE
button at the bottom of the main form; the map will be centered on the
location currently selected or specified in the Location area. If the Rise and Set
Times radio button is selected, the date will be set to the Start
Date; if the Sun and Moon Positions radio button
is selected, the date will be set to the Date in that area.
Both the Az/Alt Tool and TPE are useful for determining values to be
given when using the Sun/Moon
Search Criteria. If a search is done for a location with many possible
camera positions, these tools can also be useful for finding the optimal
camera position once potential dates have been identified. If you
don’t need to include the heights of man-made structures, TPE has
the advantage of showing the Sun and Moon data as well as the directions
to the features of interest.
Several mobile applications, including
The
Photographer’s Ephemeris,
PlanIt! for Photographers,
PhotoPills, and
Sun Surveyor,
are also available.
Most of the apps allow determination of azimuth and altitude; some allow
adjustment of looked-up elevations and allow specification of heights of
man-made structures. All are usually much easier to use on a tablet
than on a phone.
The introduction of digital mapping software in the mid-1990s
revolutionized outdoor photography planning for those photographers who
recognized its potential. In particular, the better applications could
calculate azimuth and distance between two points.
But most people didn’t need this feature, and by the late 2000s,
simpler (but free) online digital maps such as those by Google and Bing
provided competition that the desktop applications could not match.
National Geographic TOPO! was discontinued in 2012; Delorme Topo North
America was discontinued shortly thereafter. But both products can
still be useful if used copies can be found; the latest versions work
fine on Windows 10.
Trimble Terrain Navigator Pro is
still available, but it is intended for professional GIS applications,
and is prohibitively expensive for most photographers.
Unlike applications written for photographers, the early desktop
applications did not calculate altitudes. But they could provide the
elevations of features and camera positions; if distance and the
elevation difference between two points is known, the altitude is easily
calculated.
If h is the altitude in degrees, Δy is the
elevation difference in feet, and D is the distance in miles,
the altitude can be calculated to good approximation by
Slightly more accurate results can be obtained with geodetic calculations.
Unfortunately, values for elevation vary, even among presumptively
reliable sources. In the United States, the most reliable values are
usually from
monument data
sheets provided by United States
National Oceanic and Atmospheric Administration’s National Geodetic Survey; however,
accessing them can be tedious, and they are available for only a few
locations, such as major geographical features. When using other
elevation data, you should be aware that they may not be exact, and you
should be prepared to make slight adjustments to camera positions as a
Sun or Moon event approaches.
If the latitudes, longitudes, and elevations of two points are known,
the azimuth and altitude from one point to the other can be calculated,
often to greater accuracy than possible with either field measurements
or mapping software. The US National Oceanic and Atmospheric
Administration’s National
Geodetic Survey have an online
calculator that will perform such a calculation, known as the
geodetic inverse; a PC (Windows® and MS-DOS®) version
of the program is available for download.
Latitude, longitude, and elevation can often be obtained from
topographic mapping software or a printed map; if the camera position is
not easy to pinpoint on a map, GPS coordinates can improve accuracy,
though the elevation from a GPS is usually not as accurate as that
obtained from a map. For man-made features, the feature height must
usually be added to the elevation obtained from the software.
At first glance, geodetic calculations may seem daunting. But the
effort required isn’t much greater than that with some mapping
software if you need to calculate altitudes. And the accuracy is the
best of all approaches if the positions of the camera and the features
are accurately known.
Let’s use a geodetic inverse calculation to find the azimuth and
altitude of California’s Mount Williamson from the cemetery at the
Manzanar National Historical Site. For a well-defined feature such as a
summit, the US Geological Survey GNIS database is a good source for
coordinates; the search result for Mount Williamson gives
Lat: 363922N
By default, lat/lon are in packed DMS format; unfortunately,
the GNIS packed DMS format differs slightly from that for the NGS
calculator. The GNIS search page has an Advanced Search that allows
latitude and longitude to be displayed in either decimal or DMS format;
the former is easier to use in conjunction with the NGS INVERS3D
calculator. With decimal format, the search yields
Lat: 36.6560456
Lat: 36.725401
Here Google Earth is set to show lat/lon as decimal degrees; this is the
easiest format to use with the NOAA NGS calculator.
Let’s use the NGS online calculator; go to the NGS INVERS3D
Computation page, and ensure that the default Geodetic
coordinates is selected.
Acceptable input formats are indicated at the top of the form. Note
that west longitude is positive; east longitude must
be indicated by prepending an ‘E’ to
the value. The calculator’s handling of the longitude sign is
unusual; though it takes a minus sign as indicating south latitude, it
ignores a minus sign for longitude, so that either 118.3112048 or -118.3112048 would
indicate a west longitude.
The NGS calculator is also fussy about its packed DMS format, which
differs slightly from the USGS GNIS format. If you use DMS format, the
lat/lon for Mount Williamson must be entered as ‘N363922.0’ and ‘W1181840.0’ (or minimally as ‘363922.’ and ‘1181840.’). For north latitude or west
longitude, the prepended hemisphere indicator is optional; for south
latitude or east longitude, the hemisphere indicator is required. The
decimal point is required in all cases. It’s obviously easier to
use the decimal format from the GNIS Advanced Search and directly copy
and paste ‘36.6560456’ and ‘118.3112048’.
Note also that elevations are in meters.
Enter the values for Manzanar as the FROM station and the values for
Mount Williamson as the TO station; including names is helpful if you
want save the results and know what the two stations are. Click the Compute Three-Dimensional Inverse button at the
bottom of the form and get the results shown in Figure 34.
Output from INVERS3D
Only two of these results are needed: the forward azimuth and the
apparent zenith distance; unfortunately they’re not in the most
convenient format. Convert the forward azimuth from DMS to decimal
degrees to get 239.9591°. Convert the apparent zenith distance from
DMS to decimal degrees to get 78.3660°; subtract this from 90°
to get the altitude of 11.634°.
Clearly, it’s usually much easier to obtain the azimuth and
altitude using mapping software such as
the Sun/Moon Calculator Az/Alt Tool, The Photographer’s
Ephemeris Web App, or one of several mobile
apps.
When calculating the altitude of a man-made feature, the height of the
feature must be added to the base elevation. Heights and illustrations
of many tall buildings and other structures in major cities can be
obtained from the Skyscraper
Page; heights can also be obtained from Emporis or the Council on Tall Buildings and Urban
Habitat’s Skyscraper Center;
the CTBUH is internationally recognized as the arbiter of the criteria
on which tall building height is determined.
For personal use, you may do whatever you wish with the downloaded
files, including modifications, but there are restrictions on commercial
use, posting, redistribution, and claims made for derivative works; see
the section Legal in the
Sun/Moon Calculator Reference for more information. If you modify the
JavaScript file, such as to add locations to the internal database, you
should read the file Readme.txt included in the distribution on how to
have these changes recognized.
© 2008–2023 Jeff Conrad
User Preferences
Setting the Location
Selecting a Location from the Database
Searching the Database for a Location
Looking Up a Location Using an Online Service
Specifying Location Properties
Locations are Remembered
Basic Calculations: Rise/Set Times and Sun and Moon Positions
Getting the Times of Rise and Set for One Day
Getting the Times of Rise and Set for More Than One Day
Getting Sun and Moon Positions for Times Throughout the Day
Active and Inactive Inputs
Data Entry and Validation
Range is 0 to 48 hours
Advanced Calculations: Sun/Moon Search Criteria
Getting the Times of Rise and Set When the Horizon Is Not Level
![[Image: Sun/Moon Search Criteria form for Elevated Horizons]](images/ElevHorizSearchCriteria.png "Click to enlarge image")
Finding Dates on Which the Sun or Moon Rises or Sets in a Particular Direction
![[Image: Sun/Moon Search Criteria form for Sunrise Azimuth]](images/SunriseAzRangeSearchCriteria.png "Click to enlarge image")
Finding Dates on Which the Moon Rises Close to Sunset
![[Image: Sun/Moon Search Criteria form for Moonrise near Sunset]](images/MoonriseNearSunsetSearchCriteria.png "Click to enlarge image")
![[Image: Sun/Moon Search Criteria form for Moonrise with Sun Altitude Range]](images/MoonriseWithSunAltRangeSearchCriteria.png "Click to enlarge image")
Finding Dates of “Supermoons”
![[Image: Sun/Moon Search Criteria form for “Supermoon” Rise near Sunset]](images/SuperMoonriseNearSunsetSearchCriteria.png "Click to enlarge image")
Finding Dates on Which the Sun or Moon Is Near a Natural or Man-Made Feature
Get Information about the Location
Choose a Composition
Use the Sun/Moon Calculator to Find Dates
Example 1: An Urban Setting with Tight Alignment Criteria
Event: San Francisco Moonrise
Location Data and Alignment Criteria
![[Image: Az/Alt Tool, San Francisco]](images/AzAltTool.png "Click to enlarge image")
![[Image: Red map marker]](images/red-square.png){kind=small}
),
and drag it to the bottom of Columbus Avenue (it’s the diagonal
street near the top center of the map). Click on the blue
“From” marker (![[Image: Blue map marker]](images/blue-dot.png){kind=small}
)
and drag it to Lincoln Boulevard near Long Avenue at the northwest end
of the city, just west of Crissy Field; for this location to be visible,
you may need to allow the map to scroll slightly while dragging the
marker.
Center the map on the “To” marker by clicking on the
“To” marker image next to the Swap
button in the information area at the top of the map; zoom to the
highest level to aid in precisely positioning the marker. For greater
accuracy, change to satellite imagery by clicking the control at the
upper right of the map, and again zoom to the highest level; drag the
marker until it is centered on the base of the Transamerica Building.
Enter 853 for the height.
Center the map on the “From” marker by clicking on its image
next to the Fit button in the information area;
you may need to zoom out slightly to include the desired location in the
map. Adjust the marker so that it is slightly northeast of the
intersection; enter 5 for the height of the camera.
You should get something like Figure 8 (just
outside a bicycle path is arguably not the best place to set up a
camera, but the path did not exist until near the end of the period to
be searched, so for most of that time, the location posed little
hazard).
![[Image: Lincoln Blvd. at Long Ave., San Francisco]](images/Lincoln@long.png "Click to enlarge image")
![[Image: Azimuth and Altitude to Transamerica Building]](images/SFMriseAzAltTool.png "Click to enlarge image")
![[Image: Alignment of Moon with Transamerica Building]](images/SFMriseLimits.jpg "Click to enlarge image")
User Preferences: Separate Windows for Rise/Set Times and Positions
Setting the Location
Setting the Sun/Moon Search Criteria
![[Image: Sun/Moon Search Criteria for San Francisco Moonrise]](images/SFMriseSearchCriteria1.png "Click to enlarge image")
Setting the Search Dates
![[Image: Main Form: Find Dates for San Francicso Moonrise]](images/SFMriseMainFormTimes.png "Click to enlarge image")
Running the Search
Preliminary Results
Specifying a Time Difference
Refined Results: Analyzing Potential Dates
![[Image: Results of Refined Search]](images/SFMriseDates.png "Click to enlarge image")
![[Image: Main Form: Calculate Positions for 13 August 1992]](images/SFMriseMainFormPositions1992.png "Click to enlarge image")
![[Image: Sun and Moon Positions for 13 August 1992]](images/SFMrisePositions1992.png "Click to enlarge image")
Choosing the Better Date
Using Sun Altitude Rather than Time Difference
![[Image: Sun/Moon Search Criteria for San Francisco Moonrise]](images/SFMriseSearchCriteriaSunAlt.png "Click to enlarge image")
Example 2: A Natural Setting with Broad Alignment Criteria
Event: Mount Whitney Moonset from Movie Flat
![[Image: Potential Moonset on Lone Pine Peak and Mount Whitney from Movie Flat]](images/WhitneyMoonsetLimits.jpg "Click to enlarge image")
Azimuth and Altitude Ranges
Time Relative to Sunrise
Setting the Location
Setting the Sun/Moon Search Criteria
![[Image: Sun/Moon Search Criteria for Mount Whitney Moonset]](images/WhitneyMsetSearchCriteria.png "Click to enlarge image")
Setting the Search Dates and Running the Search
![[Image: Main Form: Find Dates for Mount Whitney Moonset]](images/WhitneyMsetMainFormTimes.png "Click to enlarge image")
![[Image: Dates in 2016 for Mount Whitney Moonset]](images/WhitneyMsetDates2016.png "Click to enlarge image")
Analyzing Results
![[Image: Mount Whitney Moonset: Sun and Moon Positions on 23 April 2016]](images/WhitneyMsetPositions160423.png "Click to enlarge image")
![[Image: Mount Whitney Moonset: Approximate Moon Path on 23 April 2016]](images/WhitneyMsetPath160423.jpg "Click to enlarge image")
![[Image: Mount Whitney Moonset: Approximate Moon Paths for 2016]](images/WhitneyMsetPaths2016.jpg "Click to enlarge image")
Moon Positions with Search Criteria
![[Image: Mount Whitney Moonset: Sun and Moon Positions on 25 March 2016]](images/WhitneyMsetPositions160325.png "Click to enlarge image")
![[Image: Mount Whitney Moonset: Sun and Moon Positions on 17 September 2016]](images/WhitneyMsetPositions160917.png "Click to enlarge image")
Lighting Direction
Example 3: A Natural Setting with Many Possible Camera Positions
Event: Mount Williamson Moonset from Manzanar
Alignment with Mount Williamson
Time Relative to Sunrise
Setting the Location
Setting the Sun/Moon Search Criteria
![[Image: Sun/Moon Search Criteria for Mount Williamson Moonset]](images/WilliamsonMsetSearchCriteria.png "Click to enlarge image")
Setting the Search Dates and Running the Search
![[Image: Main Form: Find Dates for Mount Williamson Moonset]](images/WilliamsonMsetMainFormTimes.png "Click to enlarge image")
Analyzing Results
Finding Locations for Potential Dates
![[Image: The Photographer's Ephemeris, Manzanar, CA, 5 May 2015]](images/TPEManzanarTerrain.png "Click to enlarge image")
![[Image: TPE: Location to Align Mount Williamson with Bottom of Moon on 5 May 2015]](images/WilliamsonMsetTPE.png "Click to enlarge image")
![[Image: TPE: Angle between Sunlight and Direction to Mount Williamson]](images/WilliamsonMsetTPEextended.png "Click to enlarge image")
Manzanar Cemetery Obelisk
The obelisk in the cemetery is one Manzanar’s most iconic
features, and you might want to include it in an image. Doing so
requires a camera position fairly close to the obelisk, leading to far
more restrictive criteria for azimuth and altitude. Using alignment
criteria similar to those above, a search of the same 30-year period
results in only three dates, ranging from 2028 to 2035. As always,
using broader alignment criteria—Other Potential Locations
Overly Restrictive Criteria
Applying Search Criteria to Positions
Using Position Search for a Date Found from Searching Rise and Set Times
Using Position Search to Find When the Sun or Moon is at a Certain Altitude or Azimuth
Example 4: Finding the Times when the Sun is at a Certain Altitude
![[Image: Sun/Moon Search Criteria for Sines Sun Altitude]](images/SinesSunAltitudeCriteria230510.png "Click to enlarge image")
![[Image: Results of Sines Sun Altitude Search]](images/SinesSunAltitudeTimes230510.png "Click to enlarge image")
Example 5: Finding the Times when the Sun is at a Certain Azimuth
![[Image: Sun/Moon Search Criteria for Sines Sun Azimuth]](images/SinesSunAzimuthCriteria230510.png "Click to enlarge image")
![[Image: Results of Sines Sun Azimuth Search]](images/SinesSunAzimuthTimes230510.png "Click to enlarge image")
True North vs. Magnetic North in Searches
Other Calculations
Observing Changes in the Times and Azimuths of Sun Rise and Set Throughout the Year
Observing Changes in the Times and Azimuths of Moon Rise and Set Throughout a Month
Observing a Thin Crescent Moon
![[Image: Crescent Moons in Lynchburg, Tennessee for April 2019]](images/LynchburgCrescents1904.png "Click to enlarge image")
![[Image: New Crescent Moons in Lynchburg, Tennessee for 2019–2020]](images/LynchburgNewCrescents19-20.png "Click to enlarge image")
![[Image: New Crescent Moon in Lynchburg, Tennessee on 5 May 2019]](images/LynchburgNewCrescent190505.png "Click to enlarge image")
Height Above Horizon
User Preferences
Window Behavior
Location Search
Time Display
Azimuth Display
Elevation and Height Units
Miscellaneous Options
Printing and Saving Results
Printing
Saving Results to a File
Popup Blockers
Most modern browsers block popup windows that are not directly opened by
the user. The Sun/Moon Calculator sends results to a new window or tab,
so the popup blocker may prevent the results from being displayed. If
this happens, set the browser to allow popups from
www.largeformatphotography.info; setting the browser to
allow popups from all sites is usually not a good idea.
Script Timeout
Running the Sun/Moon Calculator as a Local Application
If desired, the Sun/Moon Calculator can be downloaded and run as a local
application; this can be handy if you expect to be in an area without
internet access. Without internet access, web-based services such as
location lookup and weather will be unavailable, but a location in the
built-in database may be close enough, and as a last resort, the
location properties can be entered manually.
file:// URL, making Sun/Moon Search Criteria and
User Preferences forms
unusable when the Sun/Moon Calculator is run as a local application; if
you attempt to open either form, you will get the error message
--allow-file-access-from-files switch when starting Chrome.
Under Windows, this can be done by creating a shortcut and including the
switch in the shortcut. For example, the Target of the shortcut might
be something like
Chrome PATH\Chrome.exe --allow-file-access-from-files
SunMoonCalc PATH\SunMoonCalc.htm
about:config in the browser address bar. You
should get a page that warns This might void your
warranty!; click I accept the risk to
continue. Search for either
security.fileuri.strict_origin_policy or
privacy.file_unique_origin; toggle the value to
false by double clicking. Changing the latter value is
supposedly safer, but the capability may be removed in the future.
about:config to its default value.
Determining Azimuths and Altitudes of Natural and Man-Made Features
Field Measurements
Mapping Software
The Sun/Moon Calculator Az/Alt Tool
The Photographer’s Ephemeris Web App
Mobile Device Apps
Other Software
Elevation Data
Geodetic Calculations
Lon: 1181840W
Elev: 4384 m (14383 ft)
Lon: −118.3112048
Elev: 4384 m (14383 ft)
Lon: −118.162601
Elev: 1208 m
First Station : Manzanar cemetery
----------------
X = -2416156.5334 m LAT = 36 43 31.44360 North
Y = -4513184.1151 m LON = 118 9 45.36360 West
Z = 3793734.3329 m EHT = 1208.0000 Meters
Second Station : Mount Williamson
----------------
X = -2431234.1875 m LAT = 36 39 22.00000 North
Y = -4513194.9405 m LON = 118 18 40.00000 West
Z = 3789463.4915 m EHT = 4384.0000 Meters
Forward azimuth FAZ = 239 57 32.7888 From North
Back azimuth BAZ = 59 52 13.3457 From North
Ellipsoidal distance S = 15338.9277 m
Delta height dh = 3176.0000 m
Mark-to-mark distance D = 15670.8601 m
DX = -15077.6541 m DN = -7684.2298 m
DY = -10.8254 m DE = -13287.5272 m
DZ = -4270.8414 m DU = 3157.5449 m
Zenith (mk-to-mk) ZD = 78 22 32.91
Apparent zenith distance = 78 21 57.49
Heights of Man-Made Features
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