This week in What’s Up is another lesson, but it’s not how to use your telescope. There are many things beyond the natural wonders of the universe to see in the night sky. There are some problems with mega-constellations, as we mentioned in our last show, but there is something neat about seeing a batch of newly launched Starlink satellites cross the sky one after another in short succession. This week is all about how to spot satellites.

The brightest satellite in Earth’s orbit is the International Space Station (ISS), with its thousands of square meters of solar panels reflecting sunlight every which way. If you have a good-sized telescope and can track it, you can see the fine detail of its structures, but that’s really challenging. Even binoculars can begin to resolve it. To the unaided eye, it’s just a dot like a star but one that moves much much quicker and is brighter than everything else in the sky, except the Moon. 

Most of the satisfaction I get from watching satellite passes is not the visual interest, though the old Iridium flares were amazing, but by knowing that the dot does a useful task like gather data for weather forecasting or keeps a handful of people alive just outside the bottom of our gravity well.

In order to try visual satellite observing, however, you don’t need a lot of fancy equipment. All you really need is a watch to tell what time it is, a good idea of where the various compass points are, and pass predictions for where and when you’ll be observing.

There are many websites and apps that can help you know where and when to look for satellite passes. In my opinion, the best website is Heavens-Above, located at www.heavens-above.com. It has been around for a long time and is free to use. You can sign-up for a free account and tell it where you’ll be observing from, and it will provide you with a list of passes. Each satellite pass will include the name of the satellite, the time it will become visible, the maximum elevation above the horizon it will be (generally speaking, the higher the better), and the time it will disappear. It will also give you an indication of the direction it will travel, and you can even get a skymap depicting the pass.

Smartphone apps can range from free to quite expensive. Most of them will detect where you are and give you a list of the upcoming passes along with similar information to what you have on Heavens-Above. Some of them even have an augmented reality mode where you can point your phone at the sky and see an overlay of the pass. Another common feature is the ability to set an alarm for an upcoming pass.

As I mentioned, the International Space Station is the brightest man-made satellite that orbits the Earth, so it’s a great choice for your first attempt at visual satellite observation. In fact, NASA has set up a website dedicated to telling people how they can observe the ISS from where they live.

If you go to spotthestation.nasa.gov – and we’ll put that link in our show notes – you’ll find all sorts of information and resources that will help you watch it pass over. There’s a map that allows you to pick where you live and then see when the next passes will start, how long they will last, how high above the horizon the pass will be, and where it will appear and disappear. You can even sign up for email or text alerts that will let you know when passes that will be at least forty degrees above the horizon.

And if you’re curious as to where the ISS is right now, the Heavens-Above website also offers a 3D visualization showing the current attitude of the ISS and where it is above Earth.

Regardless of whether you use a website or an app to see a satellite pass, or you just want to look at the stars, be sure to go outside some clear evening and look up. Who knows what you’ll see!

More Information

Spot the Station (NASA)