Since I was little kid, I have been attracted with astronomy things, like watching constellations and just learning what’s going on up there, so when I start with photography I one the first lens I bought was a cheap Opteka 650mm – 1300mm. It was incredible how far I could get with that I remember watching the moon for hours and hours, I was just so impressed with how close I was able to see the moon by myself.
One day, back in Venezuela , when I was in high school some people from some sort of astronomy class give us like a presentation and invited us that night to come and learn by our self how to watch things in the dark sky.
I remember having my camera with the big lens that night trying to watch stars and planets from the football field of my school, suddenly one of the professors said loud, look guys! Do you guys see that little yellow start moving very smooth and slow? I yell yes! I see it! What is that? He said to us, that’s The International Space Station, and there are a few astronauts working up there making research and experiments. I was really confused about that, like are there people living in the space? I asked that too many times in my head that I couldn’t believe it. With the years I kind forget about the ISS itself, I knew there was a satellite going around us because I make a lot of research after that class, but I never paid too much attention to it because it was just impossible to my eyes see that thing going to fats around us, even with my big lens it would be impossible to see it in the dark sky, I could only see the yellow dot like it was a start.
Many have seen the International Space Station glide across the dark sky in the hours after sunset or before sunrise while it is still lit by the sun. For most locations, visible passes occur at least every few days and sometimes more than once per night. Several years ago, some clever folks at www.transit-finder.com created a way that anyone can enter their location and find a place near them where the ISS would appear to fly directly in front of the sun or the moon. When such a “transit” occurs, the path of visibility is very narrow…only a few miles at most. The timing is also very critical… orbiting at over 17,000 miles per hour, the ISS usually takes only one second or less to cross the moon or the sun. Attempting to photograph a transit can be done with minimal equipment and is a brilliant way to demonstrate the science of orbital mechanics.
The Transit-Finder website allows one to specify how far from their home they are willing to go to photograph a transit. It shows the path of visibility on a map or satellite view with the ability to zoom and move around to find a good location to set up. Try to pick a location in the center of the path for a transit that will cross over the center of the moon or the sun and for the longest transit time. A hundred yards, either way, make a definite difference, so be picky about your location. The data at the website is updated frequently due to small changes in the orbital path and altitude of the ISS, so check before you go to your chosen site to be sure that nothing has changed. I found that over the course of an afternoon the prime location for me and my partner’s latest attempt changed by about fifty yards and the time changed by one-tenth of a second.
A telescope is not required if you have a lens with a long enough focal length to make the moon or the sun occupy at least half of your field of view. Obviously, for the sun, a solar filter will be required. Generally, the apparent size of the ISS will be around one arc-minute, so it will appear to be about one-thirtieth of the diameter of the moon/sun. If your imaging scale is such that you have a small image of the moon/sun, then the ISS may not clearly be distinguishable. A 2X teleconverter may be helpful to increase your total focal length. For a DSLR that uses a crop-frame sensor (most consumer models), a focal length between 600 and 1000 mm would be desirable. For a full-frame DSLR, a bit longer focal length is required. A small refracting or Schmidt-Cassegrain telescope of the proper focal length is ideal for this.