How to Photograph Satellites: Caputuring the ISS and an Iridium flare with Your Camera
Have you ever wanted to take a picture of the International Space Station and the Space Shuttle flying over? How about capture an Iridium flare? Using the tips below I will show you all you need to know to get started with taking pictures of satellites.
What Can you Photograph?
I have to start off by apologizing if I have mislead you already. I will not be showing you how to get a crisp picture of the International Space Station (ISS) with all of the arms and modules in plain view. That takes a little bit more equipment, timing, and expertise than this article is going into. Instead, I am going to show you how to photograph the ISS as a bright streak across the sky as it passes over your head in a matter of minutes. The other type of satellite that you can photograph, with the proper planning, is an Iridium flare. An Iridium flare occurs when the geometry of an Iridium communication satellite predictably reflects sunlight towards the earth. These flares last only a few seconds but are extremely bright and satisfying to capture with a camera.
When will the ISS pass over head or an Iridium flare occur?
One of the best websites available for predicting when either an Iridium flare will occur or when the ISS will pass over is Heavens Above. The first thing that you should do at the site is to create a (completely free) account by clicking on “Create new user account” under the “Configuration” section. This is not completely necessary, but if you have the intention on coming back and using the site often, it will save you from entering your location every time. For maximum accuracy you should enter your exact Latitude and Longitude but selecting it from their database or the map is also acceptable.
Using your entered location, we can now see when the ISS will pass over next. Under the “Satellites” section on the site’s main page, click on “10 day predictions for: ISS”. Here you will be greeted with 5 main columns: Date, Mag, Starts, Max. altitude, and Ends. The magnitude of the particular ISS pass describes how bright it will be. The lower the number is, the brighter it will be. For example, the brightest star in the night sky, Sirius, has a magnitude of -1.47. The extremely bright Venus has a maximum magnitude of -4.6. The brightness of the ISS on any given pass over the earth depends on its geometry and illumination from the sun and generally varies from ~-4(brightest) to ~0.5. The other three columns describe where the ISS will be when it becomes visible, reaches its maximum height, and when it is no longer visible. It shows the time at which this will occur and the ISS’s position (Altitude (Alt.) and Azimuth (Az.)). The altitude is the angle from the horizon where 0 would be the horizon and 90 would be straight up. The azimuth uses normal compass directions. Finally if you click on the date of one of the ISS passes it will bring you to a printable page with much more detailed information. At this page they arm
you with additional information such as a more specific azimuth value and star chart defining the ISS pass with respect to the stars and planets. With this information, you now know exactly when and where the ISS will pass over your location.
To predict when an Iridium flare will occur from your area, click on either “next 24 hrs” or “next 7 days”. Once again, the magnitude is the apparent brightness of the flare. These flares vary from ~ -0 (dimmest) to ~ -9 (brightest) depending on the geometry of the flare. The altitude and azimuth are the same as for the ISS passes. The information in the “Distance to the flare centre” and “Intensity at the flare centre” describe where (with respect to your position) the flare would be the brightest and just how bright it would be. Unless you want to hunt out the brightest flare, you can
ignore this. Just like with the ISS info, if you click on one of the Iridium flare times it will bring you to another page with more information. Here you will get a confirmation of your position, when and where the flare will occur, including a small drawing of your position in reference to the flare centre. Armed with this information we can get out there and photograph these satellites!
Photographing the ISS and Iridium flares
Equipment and Getting Started
There are a couple of essential tools for satellite photography. A tripod is an obvious necessity for any night-time photography, and satellites are no exception. A cable release or means of keeping the shutter tripped on BULB mode is essential for exposures longer than the cameras default maximum length (usually 30 seconds). Although not necessary, a compass helps in finding the exact direction you should be looking in order to catch those Iridium flares.
Before we get started I should mention that in all cases it is best to put you camera on manual focus and focus the lens to infinity. Especially in dark skies it will be nearly impossible for your camera to autofocus in the dark. As well, in all cases I am working in full manual mode on my camera. Your camera DOES NOT know what you want you are trying to do for this kind of photography and you need to play around with all three controls. There are two main types of satellite images you can make: images where the stars rotate in the background (star-trails) and those where the stars do not move (pin-point stars).
Superimposed on star-trails
Superimposing your satellite image on a background of star trails is the easiest method since you don’t have to worry about keeping your exposure times short and precisely timed. In this case you are taking a long exposure with your satellite event happening sometime during that long exposure. In my experience, ~ 5 minute exposures are long enough to see the stars coherently rotating, include a ISS pass or Iridium flare without worrying about timing, and short enough that you can do a couple of test shots before hand if you want. The first thing you want to do is frame the image the way that you want it to be. Personally I like to try and include some foreground interest so that the image is not just sky. In order to verify that your image is framed the way your want it, take a test shot just long enough to get the stars
exposed (and your foreground). Since this is a test image only, I use a high ISO and an open (low number) aperture. Once the image is set up properly, bring down the ISO to a lower level (100 or 200 will probably work) and close your aperture a bit (make the number bigger). This way you can set up your long exposure, without overexposing your sky. Take a couple of test shots with the same settings you intend to use for the satellite before it comes. Once you are happy with how the image is going to look, time your next exposure accordingly. For an ISS pass, you can either start your exposure before the Space Station is supposed to be visible (so you don’t miss anything), when you see the ISS appear, or part of the way through your frame. Similarly, you can stop the exposure after the ISS pass is done, when you know it is out of the frame, or even part of the way through the frame. For an Iridium flare, plan the flare to be somewhere in the middle of your exposure to be sure that you
include it. For example, for a 5 minute exposure, start at least 1 minute before it is scheduled. In both cases, make sure you use the exposure times you planned for. Resist the temptation to stop the exposure early to see how your image turned out. You made those test exposure times for a reason!
Getting an ISS pass or an Iridium flare on a background of pin-point stars has all the same principles as for the star trails image but with two main challenges: exposure time, and timing. Getting the an appropriate exposure time depends on the lens that you are using. The wider the lens, the longer exposure you can expose before star trails become apparent. I have found (on a cropped sensor) that at ~17mm you can use an exposure time of ~30 seconds without significant star movement. Once you have this exposure time you need to adjust your ISO and aperture accordingly so that
your sky is properly exposed. With respect to timing for an Iridium flare, you can either wait until you see the beginning of the flare (and risk missing the start of the flare) before starting the exposure or try to start it a few seconds before the flare is scheduled to be seen. If you use your exact coordinates in heavens-above and a cell phone or computer clock, it is surprisingly accurate.
What I have just explained should have given you the basic information needed in order to get out there and not only see the ISS flying overhead, but also take amazing pictures of it fairly easily. Photographing an Iridium flare can be extre
mely satisfying considering how briefly it is visible in the sky. Remember, this tutorial is only the tip of the iceberg and I am only describing the techniques that seem to work for me. As with all astrophotography, not even the sky is the limit.
This post is part of the series: Adventures in Night Photography
In this series you will find articles to satisfy your creative night photography needs. You will learn tips, tricks, and ideas on how to photograph the moon. You will learn the ins and outs of taking pictures of constellations. Finally, you will learn how to photograph satellites.