Astrophotographers all know that frustration. You set up your gear, you get ready for a multi-second or multi-minute exposure photograph, and you capture your desired object perfectly. However, when you get cozy again beside your computer — there’s that awful streak. You see that slice of human ingenuity, an artificial satellite, a beam of light cutting across your precious image.
With thousands of objects circling the Earth and dozens more launching each month, this problem is more and more common. Here are a few tips to avoid satellites while taking pictures.
Check the web
The first item is being prepared — knowing when satellites are most likely to streak across the sky. There are numerous websites to assist you with this. One catch-all website popular with amateurs is Heavens-Above.com, which publishes the orbits of the International Space Station, SpaceX’s Starlink satellites and other satellites, well-known and obscure. Alternative websites are N2YO.com and CalSky.
If you prefer to use your phone, one popular app possibility is ISS Detector for Android and iOS by RunaR. The basic version includes satellites such as the International Space Station (ISS) and any remaining Iridium flares from those satellites, and you can purchase in-app for more satellite possibilities. Remember — use red-light mode or cover your phone with red filters before bringing it outside in the dark, lest you ruin your light vision (or someone else’s). Depending on the star party, it might be best to avoid using the phone altogether.
Check the time of day
Most astrophotographers prefer to take photos at the darkest time of night, also known as astronomical twilight. That’s when the Sun has dipped at least 18 degrees below the horizon, allowing for maximum darkness and the ability to see the dimmest objects. Fortunately, satellites do not appear as frequently during these times, as the Sun is far below the horizon.
The real time to avoid for satellite streaks is around dawn and dusk, when the satellites are prone to catch the Sun’s light and reflect it down to the ground, which is where you are. A train of launching Starlinks in particular can look very bright, making it all but impossible to see anything astronomical behind. (SpaceX has pledged to dim the satellites in the future, fortunately.)
Check the launch schedule
When satellites are just being launched into space, they are low to the ground and — at times — orbiting alongside their rocket stages that also catch the light. Fortunately, most launches are well-published ahead of time. Spaceflight Now has a launch schedule for objects launching around the world, whether they be from the United States, Europe, Japan, Russia or other locations.
At times, however, countries do choose to keep launches private for national security reasons, or simply because they don’t feel ready to announce the launch until after it has succeeded. Your best bet is to monitor space news in the hours before you go outside, as sometimes rumours of upcoming launches make their way onto local forums and then, the mass media.
Elizabeth Howell (Ph.D.) is a Canadian space journalist who has been obsessed with the topic ever since she, as a young teenager, saw the movie Apollo 13 in 1996. She grew up wanting to be an astronaut. While that hasn’t happened (yet), Elizabeth has seen five human spaceflight launches — including two from Kazakhstan — and she participated in a simulated Red Planet mission at the Mars Society’s Mars Desert Research Station in Utah.