### Sunday Oct 11, 2009 at 22:20

# The Photographer's Ephemeris

The Photographer’s Ephemeris (TPE) for Desktop is a free application for Mac/Windows/Linux designed for landscape photographers.

## Download

Get TPE for Desktop (free):

Get TPE for iOS:

## Latest News

December 23 2012: TPE 1.1.1 is now available with some new features and bug fixes. Please head over to http://photoephemeris.com/support#desktop_support for more details. In particular, there is an issue with auto-update for TPE 1.1.0: please read the note on the support page for more information.

November 26 2011: TPE 1.1.0 is now available. A few important items in this update including an updated timezone database for Europe and, in particular, Russia. We’ve also added the ability to import and export your saved locations as KML. This allows you to share location files both with other users and other applications (such as Google Earth).

As you may have noticed, I still haven’t got all the TPE material migrated over to the main site, photoephemeris.com. I built the new site in Drupal and sort of wish I hadn’t as it’s a bit of a nightmare to manage as compared with dear old Textpattern (which is what this site uses).

However, I hope to have the migration complete in the next few weeks, so much of this material will be moving over at that time.

As usual:

- TPE remains free
- There’s no expiry date (as there was during Beta)
- If you’d like to support the continued development of the desktop version, there’s a donate link on the right of this page (or consider purchasing our iOS or Android apps)

Many thanks to those who’ve offered support so far – it’s much appreciated.

Requirements
Installation
Tutorials
Using the program
Keyboard shortcuts
Configuration options
Advanced usage
Program expiry
Version history UPDATED
Some notes on how it works
Accuracy
Known issues
Feedback

## Introduction

Landscape photographers typically wish to plan their shoots around the times of sunrise/sunset or twilight, or alternatively when the moon is in a particular place in a particular phase.

While times of sunrise etc. are readily available on various sites on the internet (direction of sunrise etc. less so, but still readily found), there are fewer programs available which combine such information with a topographical map allowing the photographer to match the astronomical to the location.

A typical use might be to determine when the sun will set along the axis of a mountain valley, or when a full moon rise will rise across a lake.

The application uses Google Maps providing users the ability to select a location and determine the time and azimuth of sunrise or sunset for a given date or dates.

## So what’s new about this?

Not a huge amount – there are other programs out there that calculate the same data and more.

What I haven’t seen before is the combination of the key data together with a topographical map, courtesy of Google, in one program for either Windows or Mac.

If you’re already on location, this isn’t probably going to help. If you’re planning a trip, then perhaps this is the program for you.

## Cost

Nothing. It’s free. Help yourself.

Also, the Adobe AIR version will remain has remained free post Beta.

However, developing and maintaining it is not without costs (hosting, Geonames commercial subscription, development tools etc.). If you’d like to support the continued development of TPE, please consider a donation – there’s a link to the right of this page.

## Requirements

TPE uses Adobe AIR, so you’ll need to have that installed. You can obtain it here (for free):

Why do you need it? AIR is a framework for Rich Internet Applications – apps that combine the interactivity of the web with local programs that can run outside a browser environment. It is lightweight and unobtrusive and there is a wide variety of useful applications available that use it. Adobe AIR is compatible with Windows, Mac OS X and Linux (up to AIR 2.5).

The program requires a connection to the internet to function.

## Installation

Click here to download:

Once you’ve downloaded this file, double-click to install. I don’t currently have a code signing certificate for this application, so you’ll see scary-looking warnings about the publisher being “unknown” and program having unrestricted access to your system – you’ll have to make your own call here for now.

Adobe AIR 1.5.3 or later must already be installed (see above).

Please read the Terms of Use before installing.

## Tutorials

I’m delighted to be able to include two excellent video tutorials on TPE produced by Jared at Yellow Wood Guiding close by in Estes Park, Colorado. Estes Park is, of course, the gateway to Rocky Mountain National Park, one of the most popular of all – with good reason. Yellow Wood Guiding offers wildlife and nature tours of the park as well as photography safaris. If you’re in the area and plan on visiting the park, I encourage you to check them out.

However you prefer to learn, I’d encourage you to check out the keyboard shortcuts – I hope you’ll find they increase your productivity in TPE considerably.

### Part 1

Watch Part 1 of “How to use the Photographer’s Ephemeris” for all the basics:

### Part 2

…and Part 2 for the rest!

### If you prefer reading to watching:

Here are some tutorials you can follow through at your pace that cover pretty much all TPE has to offer:

Part 1: The Basics
Part 2: Twilight and the Details View
Part 3: Geodesy
Part 4: The Horizon

## Using the program

If you’d prefer the abbreviated instructions, and are in a hurry to get going, please read this section. The basic idea is as follows:

1) Pan around on the map to find a location you’re interested in, or drag and drop the red marker. Click the Centre button (located at bottom right of map, or press ‘C’) to place marker at the centre of the map
2) The “Ephemeris” table on the right shows you the sunrise/sunset/moonrise/moonset times (plus azimuths and phase of moon). Click the Twilight button to see twilight times instead
3) Click the up and down hands to advance dates (or press ‘P’ – previous, ‘N’ – next or ‘-’ and ‘+’ on the main keyboard), or select a different date from the date selector
4) The timezone of the location should be detected automatically and displayed at the lower right of the window (if timezone is not shown, you can click override and select manually)
5) The latitude, longitude and elevation above sea level of the current marker position are displayed at the top of the map.
6) If you want to determine the nearest place name of the current map location, click the Search button (the magnifying glass) below the map.
7) If you want to search for a specific named place, click into the location text box (left of the search button) and type the name of the place you want to find. If Google can find it, the map and marker will move to that location.
8) Click Locations (top right) and you can save your current location, or go to or delete one that you saved earlier.
9) Certain labelled terms throughout the program have glossary entries – any label that turns reddish when the mouse is over it will, when clicked, display the corresponding glossary entry. (Note – the glossary is not entirely complete yet.)
10) If the shot you’re looking for isn’t right at the moment of sunrise or moonset, click the Details button (or press ‘D’ on the keyboard) to see detailed information for how the sun and moon are positioned throughout the day and night at your selected location. The central panel allows you to set an arbitrary time of day and see azimuth and elevation angle information numerically. You can also click between the various celestial events for the day using the skip buttons. The graph shows the altitude (in the astronomical sense of angle) for sun and moon throughout the day. Those three lines below the 0° line represent the elevation angle of the sun at the various twilight boundaries: -6°, -12° and -18°.

The idea is that a photographer scouting locations would use Google’s topographic map to see the contours of the location and then, assuming they want to shoot the “golden hour” would want to see where and when the sun/moon will rise/set. The lines on the map show you the direction of sun/moon rise/set.

## Keyboard shortcuts

There are a handful of keyboard shortcuts you can use:

- E to display the Ephemeris screen
- L to go to Locations
- P or - for the previous day
- N or = for the next day
- T to toggle display of twilight information (new in Beta 0.7.4)
- D to toggle display of details information for the selected date (new in Beta 0.8.0)
- S to swap the positions of the primary and secondary map markers (new in Beta 0.9.5)
- C and Shift-C to (i) place the marker at the centre of the current map display or (ii) to pan the map to place the marker at the centre of the display
- Shift Hold down this key to extend the azimuth lines displayed on the map through the marker location. This is helpful for aligning particular landmarks, your shooting location and the direction of the sun/moon. This function only works when you are sufficiently zoomed in (otherwise, the extended azimuth line would be inaccurate and misleading)
- Ctrl + and Ctrl – to zoom in and out of the map respectively
- Shift + to add new location
- Left and right cursor keys can be used to move the Details View slider control in one minute increments – click on the slider first

## Configuration options

Units of Distance: determines units used for location elevation (metres or feet) and distance to nearest known place (km or miles)
Default location names: select preferred format for displayed location name (as shown during reverse geocoding, i.e. what’s the nearest place to here?) and default name provided when saving a location
Service timeout (seconds): determines the default timeout when querying the GeoNames web services for timezone, elevation and nearest place name. Consider increasing this value if you are seeing “Request timeout – retrying” or “Request timed out” messages. (The specified value is used as is for timezone and altitude queries, but in fact is doubled internally for reverse geocoding as this service can normally take longer to respond, particularly if the nearest known place name is some distance from your current specified location.)
Timezone management: not user editable. Checked if the timezone management database is correctly installed.
Azimuth lines: user selectable colours for the lines shown on the map indicating direction of sunrise/sunset/moonrise/moonset. The same colours are used in the Details display.

## Advanced usage

A couple of advanced features, new in Beta 0.9.5:

### When will the sun appear from behind that mountain?

Often, the sun or moon is not visible at the moment of rising or setting, due to an obstruction between the observer and the horizon. You really need to know the angle from the observer to the obstruction. In Beta 0.9.5 or later, click Details. Note the Geodetics panel located at the bottom of the Details view. Additionally, an additional map marker will appear in grey to the east of the current map location. Try dragging that marker and positioning it on a landmark near your primary location.

You will see that the data in the geodetics panel updates to show the altitude (in the astronomical sense of altitude angle) from the primary to the secondary location. Using the slider in the central panel, you can ‘pan’ the sun or moon around to see what altitude it will be at at the time it passes through the same azimuth as the obstacle where the secondary marker is located. When a positive apparent altitude angle is shown in the geodetics panel, a line is also added to the details graph above representing that altitude, making it easy to see where to set the slider for the moment the sun or moon matches that altitude (although there’s no guarantee the azimuth will match the bearing at that same time).

In addition, you can determine an accurate distance and bearing between the two map marker locations and also the difference in elevation above sea level.

### Can’t you see farther from a mountain-top?

Yes. Because you can see farther, you’ll see the sun rise in the east sooner too. This is due to the fact that you are elevated above the horizon. The height above the horizon determines the “dip of the horizon”. Knowing the dip of the horizon, we can adjust the rise and set times of the sun and moon accordingly (rise gets earlier with height, set gets later).

In Beta 0.9.5 (or later), the program will factor all this in for you. There are two ways to use this (i) manual and (ii) automatic. In manual mode, you can type a number into the text box below the map at the left side: this should be the elevation above sea level at the horizon. For example, if you are standing on top of Longs Peak, Colorado looking east, you can see from a topographical map (or from first-hand knowledge) that the horizon lies many miles away where the land lies no more than 5,000 ft above sea level. In this case you enter ‘5000’.

The program knows (in general) the elevation above sea level of your primary location. Taking the difference, the dip of the horizon can be calculated and the rise and set times adjusted accordingly. Press the clear button to the right of the field to clear the values (in which case the times return to their default, assuming no dip of the horizon).

In automatic mode, you can lock the elevation at the horizon to the secondary marker location. This option (the pin icon at the left of the field) is only available in Details mode and only enabled once a secondary location has been specified by moving the marker. Once locked, any change to either primary or secondary location will result in the dip of the horizon being recalculated and rise/set times adjusted.

### How do I know where the horizon is?

If you are planning a trip to an unfamiliar location, you may be wondering how to determine the elevation at the horizon, or even where the horizon lies. While in theory, this could be calculated by the computer, in practice, there are too many variables. Which direction do you care about (e.g. rise or set)? How does the terrain vary in elevation between your location and the direction of horizon?

Instead of trying to second guess this, the program allows you to specify the elevation at the horizon. In automatic mode, this is taken from the secondary map marker location, as described above. Once specified, it is possible to calculate an estimated distance to the horizon. TPE shows this distance using a grey-edged circle overlaid on the map. This is drawn once the elevation at the horizon is specified and the elevation of the primary location is known.

In automatic mode, if you see the circle fall well inside the location of the secondary marker, then it’s likely you cannot in fact see as far as the secondary marker from the primary location in that particular direction. Conversely, if the circle falls well beyond the secondary marker, consider moving the marker outward in the direction you care about (e.g. the direction of sunrise) and watch the circle adjust. Depending on how varied the elevation of the terrain is, you may find yourself ‘chasing the circle’ as it appears to dodge your secondary marker. However, try it a few times and you’ll get the hang of it. Just remember: the higher the observer above the horizon, the farther away the horizon is.

Finally, you can use automatic mode temporarily to determine elevation above the horizon, then switch it off again in order to use the secondary marker to check angles to any obstacles in your shot, as described above.

### If in doubt…

If you’re uncertain about how best to use the height above the horizon features, then don’t. Just plan to arrive a little earlier for sun-rise if you’re in the mountains and to stay a little later for sunset. That’s good advice no matter how well-planned your shoot is.

However, if your shot requires critical alignment of the sun or moon at the moment of rise or set, then you might want to invest some time to investigate the possible effects of height above the horizon. But remember, actual visibility to the horizon is governed by clarity of the air, moisture content, and temperature gradients which affect the degree of refraction. None of these can be predicted for any given day with any great degree of certainty.

## Program expiry

Release 1.1.0 has no expiry date. Earlier beta version had expiry dates built-in, most recently 1.0 RC1 which expired on December 31 2009.

## Version history

This content has moved to http://photoephemeris.com/tpe-desktop-release-notes.

## Some notes on how it works

TPE is fairly simple in concept: 1) display a Google Map 2) choose a date 3) calculate and display a bunch of astronomical data.

The tricky part comes from the connection between 1 and 2. Most similar programs and web-sites have you select from a pre-defined list of locations, where, presumably, things such as the relevant time zone are already saved.

Latitude and Longitude don’t give you timezone so easily. Rather than try to write code to work that out myself (have you seen how variable the actual timezone boundaries are close up?), I’m using GeoNames web services. This is how TPE determines relevant timezone for the chosen map location, as well as elevation above sea level.

Geocoding means “find this place name on the map” – Google performs this service. Reverse geocoding means “find the best place name corresponding to this latitude and longitude” – GeoNames does this. The search button below the map does the former if you specify a place name (click in the box and type) and does the latter if you don’t.

Automatic Daylight Savings Time detection is available as of Beta 0.7.5. This is another snake pit for the programmer. Although your computer has all this information already (it probably updated itself quite happily this morning, if you’re in the US), I can’t see any way to exploit that knowledge within my program – I’d have to change the timezone of your computer, plus the system date.

Therefore, I’ve implemented the Olson Timezone Database to allow DST settings to be looked up based on the timezone you’ve navigated to and the date you select. One nice side effect: historical dates will work too – so if you’re looking for the time of that full moon in Sri Lanka before the change to Indian Standard Time in 1996, TPE will report it correctly. (However, I need to write up some more notes on validity of date ranges in the program. There are many factors to consider.)

## Accuracy

I’ve done a reasonable amount of testing of the calculated results against other programs and sites and in general, TPE agrees to within +/- 1 minute on most measurements, and is very close on calculated azimuths (that’s not sounding terribly scientific, is it? I’ll try to improve the precision of my language here…)

The solar coordinate calculations used in the program are based on an abbreviated version of the VSOP87 algorithm presented in the Meeus book (see About within the program).

Calculated azimuths show map bearing, not compass (i.e. are not corrected for magnetic declination).

Times of sunrise, sunset, moonrise and moonset may optionally be corrected for observer altitude above the horizon using the secondary marker (see Advanced Usage above). Elevation is obtained using the GeoNames Shuttle Radar Topography Mission web service (detail here). According to GeoNames:

> Shuttle Radar Topography Mission (SRTM) elevation data. SRTM consisted of a specially modified radar system that flew onboard the Space Shuttle Endeavour during an 11-day mission in February of 2000. The dataset covers land areas between 60 degrees north and 56 degrees south. This web service is using SRTM3 data with data points located every 3-arc-second (approximately 90 meters) on a latitude/longitude grid.

Documentation from NASA, including an accuracy is available here

Note that times of rising and setting are affected by many factors which cannot be calculated in advance. These include barometric pressure and temperature. As such, it is not meaningful to quote rising and setting times more than to the nearest minute.

## Known issues

- At certain latitudes and certain times of year, there may be more than one sunrise or sunset within a 24 hour period, e.g. Reykjavik in late June. TPE will only indicate one of them.

## Feedback

Please e-mail support@photoephemeris.com with your comments and feedback.

[Originally posted Mar 10 2009]

Posted in TPE

Stephen · Sunday, October 11, 2009, 22:20 · Permalink · Comment [140]

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