I saw this retweeted by my buddy @CachingCop:
For those who aren’t familiar, if you watch the night sky enough you’ll occasionally notice what looks like slow moving stars. You might notice some rather fast ones too. Both of these are not stars. But what exactly are they?First, let’s define the difference between slow and fast moving objects in the night sky. When you see them, you’ll quickly learn the difference. A fast moving object will zip across rather quickly, often appearing for only a few seconds. A slow moving object will be in view much longer, and will move at a speed similar to what you might observe from a plane passing overhead. Now you know the difference in fast or slow relative to the movement in the night sky.
If you were to see a slow moving object, it is almost guaranteed that you are seeing a man-made object. The first thing to look for is if you see any blinking lights. If you see what appears to be blinking lights, especially if it looks like there might be more than one light or the blinking is in a color other than white, then you are looking at a plane. Case solved.
But if you don’t see blinking lights, more than one light, or different colors, then there is a good chance that you are seeing a satellite orbiting our planet. Pretty cool huh. What you are actually seeing is sunlight reflecting off the panels of the satellite, not actual lights on the object. Even though it is dark out, since the object is at a high altitude, light can get around the Earth and still reflect. There is still an “Earth’s shadow” so an object at a higher altitude will have a bit larger window of time to potentially see it during the night. That window is based around sunset and sunrise. So you’ll have a harder time seeing satellites at 1 AM than you will at 10 PM.
Can you see all orbiting objects? No. Only the most reflective will be seen, and then only if they are in the right position, and angled the right way with respective to both you and the sun. Thankfully, there is some rather reliable math involved in predicting when and where you might see an object based on your position on earth. A great resource for anyone looking to spot a satellite is a website called Heavens-Above.
Heavens-Above uses data about a large collection of satellites to determine when and where in the sky you can spot one based on your position. It also only returns those that are the most likely to be seen, weeding out satellites predicted to have a lower brightness when passing. Usually, you’ll see a mix of both American and Russian satellites, and occasionally parts of rocket boosters that were used to send them up. But you’ll also get a listing of things such as the Hubble Space Telescope, Iridium Communication Satellites, and the International Space Station. When a shuttle mission has launched, you’ll start seeing times for that as well.
The nice thing is the manual entry of your location. You can get times spit out for your own yard. You only need two pieces of information (Geocachers…take note). First, get your latitude and longitude (N/S and E/W coordinates, respectively). Second, your time zone. Near the top of the page, find the Configuration heading and select “Edit Manually”. Just follow the instructions (particularly with how to enter your coordinates). Hit submit and enjoy. There is a lot of information to digest, particularly details about Magnitude, Altitude, and Azimuth, that we will cover in a future post. Those are important for knowing where exactly to look in the sky.
For those out there that use Twitter, you can get updates for when the International Space Station can be seen in your area. First, make sure your location is updated in your Twitter bio, then just follow @Twist. They use your location data, compare it against Heavens-Above’s database, and send you a tweet when the ISS might be visible for you.
But wait?!?! I mentioned fast moving objects too. What are those? Well, if you see something zip across the sky in only a few seconds before disappearing, you just saw a meteor. An actual piece of dust/rock from space. We’ll talk about meteors in the future too, but rest assured that these can be fun to spot as well.
So go check out Heavens-Above. You’d be surprised just what is actually visible.