So you’re looking up at the stars one night and you see something up there moving… suddenly it goes out. Was that a satellite? Was it an airplane?
There are a lot of websites out there for watching satellites but the best, most comprehensive and one of the oldest is www.heavens-above.com. I have been using it for almost as long as the internet itself has been around.
It’s great to know that at a certain time tonight you can step outside, look in a certain part of the sky, and maybe, just maybe, see a satellite suddenly appear and whiz by.
You will need your latitude and longitude; there are lots of ways to get that. Then go to the heavens-above site and just play around with it.
The first and easiest is the ISS, followed by the Iridium satellites. With practice you can even see the Iridiums in the daytime! The best way is to practice on these two until you get pretty good at it – then there are hundreds more. And, the site has lots and lots of other good information about spacecraft. The more time you spend there, the more things you’ll want to try.
Keep these things in mind though:
1) Your fist help at arm’s length covers about 10 degrees. Use that to measure altitude (Alt.) above the horizon.
2) The direction (North, northeast, etc.) is given as a bearing and is called “Az.”. East is 90, south is 180, west is 270, etc.
3) “Magnitude” is how bright the satellite will be. The smaller the number the brighter it is. Anything smaller (brighter) than zero will be very bright, like an airplane.
4) Airplanes often have their flashers on; satellites do not.
5) The light from a satellite is reflected from the Sun. That’s why it will suddenly appear in the middle of the sky and will suddenly go out. The website tell you exactly when these will happen.
6) The whole thing is an estimation. It’s a sort of a sport. Times may vary, usually a little later as the orbits decay unexpectedly, and magnitude can change too.