Updated: Feb 24
In 2008 a software engineer named Stephen Trainor took one of my workshops. During the workshop, I showed students how to use a ruler, a compass, a topographic map, and a bit of trigonometry to answer questions like, “What is the best day to photograph the full moon setting over Longs Peak?” Stephen thought that my approach looked useful but knew there had to be a better way to get the results I so laboriously achieved. He went home and created the first version of the Photographer’s Ephemeris, which quickly became my all-time favorite desktop planning app.
The first version was for desktops only. It was free, but you can’t make a living if you give away your work, so Stephen created paid versions of the app for iOS and Android devices. These versions had many more features, but were limited in usefulness, in my view, by the inherently small screen size of a mobile device. Maps are most useful when they’re big. I love planning my shoots on my 27-inch monitor. For years, I urged Stephen to produce a full-featured version of the desktop app, then charge for it. Last fall, it finally happened.
The basic desktop version, now called Photo Ephemeris Web, is still free, and it certainly has enough features to get you started. To fully unlock the potential of the app, however, you’ll need to upgrade to the Pro version, which costs $30 per year. The Pro version has better maps, better location search, and better position search (the ability to search for the days and times when the sun, moon, or galactic center, the brightest and most photogenic part of the Milky Way, will appear in a specific position in the sky).
A first glance, the interface for Photo Ephemeris Web Pro will look familiar to previous users of the Photographer’s Ephemeris. The Map module, the heart of the program, displays a map with colored lines radiating out from a red pin. The broad lines indicate the direction of the sun, moon, or galactic center when they rise or set. Narrow lines indicate the direction of those objects at the specific time you choose. Lighter-colored broad lines indicate the direction where the object will rise; darker broad lines indicate the direction where the object will set. For example, the direction of sunrise is indicated by a broad yellow line; the direction of sunset is marked by a broad orange line. The broad blue lines indicate the direction of moonrise and moonset; the broad gray lines indicate the direction where the galactic center will rise and set (figure 1).
Beneath the map is a timeline which again will look familiar. It has the same shortcut icons for sunrise, sunset, moonrise, moonset, etc., that the previous version used. Click an icon to set the time to the moment when that event occurs. The narrow lines indicating the current direction of the sun, moon, and galactic center will update accordingly. If a narrow line is not visible, that object is below the horizon. A time slider lets you further adjust the time. The visibility of the various elements beneath the map is controlled by icons in the top right corner of the interface (figure 1).
As in the previous version, you can click the gray secondary marker's icon, which will cause the marker itself to appear on the map. You can then drag the marker to a new location. Activating the secondary marker turns on the geodetics panel, which provides data on the relationship between the primary and secondary markers: distance, direction, change in elevation in feet, and change in altitude, which the app calls elevation angle (figure 1). The elevation angle is an object's position expressed in degrees above a level horizon.
All of these features will be familiar to long-time users of the Photographer’s Ephemeris. To see the best new features, open the new Sphere module. Here you’ll find the armillary sphere, a three-dimensional representation of the sky with colored lines representing the paths of the sun, moon, and galactic center across the sky’s dome. In addition, a series of light gray dots shows the position of the Milky Way band across the sky at the time you specify. The size of the dots indicates the relative brightness of that part of the band, with the largest dot representing the galactic center. Click, hold, and drag on the sphere to rotate it on its axis or examine it from different angles. Drag the time slider to watch dots representing the sun, moon, and galactic center move along their respective paths and to watch the Milky Way band move across the sky. “Latitude” lines on the sphere indicate zero, 6, 30, and 60 degrees above the horizon. This is useful, for example, for judging the altitude of the highest part of the Milky Way arch when planning Milky Way panorama shots. Figures 2 and 3 show why it’s much easier to shoot Milky Way panoramas in the spring, when the high point of the arch is relatively low in the sky when the galactic center is in the right position, than it is in late summer or fall. Figure 4 shows the Milky Way panorama I shot in Chesler Park on April 14, 2018—the same date and time as the armillary sphere shown in figure 2.
The Sphere module’s other new feature is Visual Search, Stephen’s name for a tool that lets you search for the day and time when the sun, moon, or galactic center will be at a specific place in the sky. Let’s use Photo Ephemeris Web Pro to figure out the best day in the next year to shoot the full moon setting over Longs Peak as seen from Twin Sisters.
The first step is to place the red primary marker atop Twin Sisters. In the Map module, search for Twin Sisters Peaks. Click Go to place the primary marker atop the summit. Now click the gray secondary marker icon on the right side of the screen to activate it. Drag the gray pin that appears on the map southwest to the summit of Longs Peak. In the geodetics panel that appears just above the timeline, note the azimuth (compass bearing) to the summit of Longs Peak. I get about 245 degrees. The moon will need to be in approximately that direction. Note also the altitude of Longs Peak as seen from Twin Sisters. Longs Peak is higher than Twin Sisters, so you have look up about 5 degrees to see the summit of Longs Peak. If the moon is in the right direction but has an altitude less than 5 degrees, it will be below the actual horizon even if it hasn’t actually set. (Rise and set times are calculated as if the earth was a completely smooth sphere, with no mountains or valleys.) Figure 1 shows all these settings.
The moon doesn’t need to be precisely over Longs Peak for the shot to work. There is some range of acceptable azimuths. Drag the secondary marker a bit left, then right, of Longs Peak and note the azimuths. Let’s say the acceptable range of azimuths is 235 to 250 degrees.
Similarly, there is a range of acceptable altitudes. The moon is quite small in an angular sense, subtending an angle of only 0.5 degrees. If the moon is too high above the horizon, you’ll need to use a wide-angle lens to include it and Longs Peak. That will render the moon as a dot. Let’s say the acceptable range of altitudes is 5 to 10 degrees.
With this data in mind, return to the Sphere module. Be sure the date is set to the current date. Enter the parameters we calculated above, as shown in figure 5. Be sure the Range box is checked. Click Search. I got 78 results. Next, click Filters to refine these results. We want the moon close to full, so click Full Moon and enter the illuminated fraction as .95 to 1 (95 to 100 percent). And we want to shoot when the light is interesting, so click Near Sunrise/Sunset and enter an altitude of -2 to +2 degrees. Both settings are shown in figure 6. Click Apply.
Now click Results (figure 7). You’ll see a list of dates with a range of times when your criteria are met. (Note that as of this writing, not all criteria will necessarily be met throughout the entire range of times.)
Let’s check the first day listed, April 27, 2021. The time range is 5:33 a.m. to 6:03 a.m. Click the first time in the range, 5:33 a.m. Return to the Map module. The thin blue line indicates the direction of the moon at that moment—right between Longs Peak and Mt. Meeker. The altitude of the moon is 10 degrees. The time, 5:33 a.m., is 34 minutes before sunrise, which is probably a bit too early for interesting color in the sky, because the sun is still 6 degrees below the horizon. (Note that the sun altitude at the beginning of the time range is outside the desired range of -2 degrees to + 2 degrees.) Drag the time slider to 5:57 a.m., 10 minutes before sunrise, when the twilight wedge is likely to peak. Now the moon is almost directly above Longs and just two moon diameters (1 degree) above the summit. If the sky at the eastern horizon is very clear, the shot could be spectacular. By sunrise at 6:07 a.m., which is four minutes after the range of times listed, the moon will be disappearing beneath the north ridge of Longs Peak.
April 27, 2021, could be spectacular, but the tolerance is tight. A narrow band of clouds at the horizon could kill the twilight wedge. You can check the remaining dates to see if any of them offer better potential—or a better safety margin. See the screenshot for August 23rd, 2021, at the top of this post (figure 1) for the moon position two minutes before sunrise on what may well be the best day of the year.
This quick summary of old and new features should get you started. To understand everything Photo Ephemeris Web Pro can do, check out the well-done tutorials found under the Tutorials tab in the app. I think you’ll agree that Photo Ephemeris Web Pro is the best desktop planning app available. To get started, go to https://app.photoephemeris.com/.
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