We’ve seen the International Space Station transit in front of the Sun and the Moon, but passing in front of Saturn is something entirely different. Nice shot!
The relative sizes and distances involved are particularly neat for this composite photo of the transit. Saturn is over a million times larger than the space station, but over three million times as far away. The resulting perspective puts them on roughly the same scale, the elongated station stretching the width of the ringed planet as it passes. The result is like seeing a child attempt to hide behind a spindly tree.
Astrophotographer Julian Wessel put a lot of planning into how to get the best shot. He used the sky calendar CalSky to plot out where he needed to be to get the right view at the right time, then the planetarium software Stellarium to visualise his shot. The weather forecast on the fateful night wasn’t the greatest — clear, but with enough instability to potentially blur his targets. He headed out anyway on January 15, 2016, set up his 10" telescope, and started shooting. It worked, producing this fabulous composite photo.
Check out a realtime video of the transit and more details on how he set up the shot in his video here:
Image credit: Julian Wessel