All you need is your phone and a place to view from — your backyard, your front step, a nearby intersection — but no telescope. Share this information with your family across the region, then do it together as a group! ISS flies over Philadelphia at least 4 times a day and as many as 7 times a day, all because of how the station orbits and how the Earth turns underneath the orbit.
The orbit is a circular path around the Earth, as the earth turns under the station, ISS orbits Earth seeing different portions of Earth on each orbit. The orbital period — the time it takes to complete one orbit — is about 92 minutes. Sometimes if conditions are right you can see two passes in one evening or morning. There are two daily time windows when the station is visible: morning and evening twilight — the period just before sunrise and the period just after sunset.
This when the background sky is dark enough but ISS is still catching enough light from the sun for us to see it. ISS orbits at an altitude of about miles and flies along at 17, miles an hour. The passes, called fly-overs, can last from under two minute for a short pass to just under 8 minutes for a full flight from horizon to horizon. Space Station appears as a bright dot about the brightness of the planet Venus.
It moves steadily across the sky getting brighter as it comes closer to your position. The flyover schedule indicates the space station is both appearing and disappearing from the same direction, how is that possible? The Spot the Station software rounds off directions to the nearest cardinal and intracardinal directions. This can result in it seeming as though the ISS will be appearing and disappearing in the same direction even though it is traveling across the sky.
This typically happens on flyovers with a short window of visibility because the ISS is quickly moving into or out of the Earth's dark shadow where, from our location on the ground, we can't observe its full pass across the sky.
How often can I expect to see the space station? The space station is visible because it reflects the light of the Sun — the same reason we can see the Moon. However, unlike the Moon, the space station isn't bright enough to see during the day. It can only be seen when it is dawn or dusk at your location.
As such, it can range from one sighting opportunity a month to several a week, since it has to be both dark where you are, and the space station has to happen to be going overhead. Why aren't there any sighting opportunities for my location? It needs to be dark where you are and the space station needs to be overhead in order for you to see it. Since the space station's orbit takes it all around the globe, it can be passing over you at times when it will not be visible- either in the middle of the day or the middle of the night.
The space station must be 40 degrees or more above the horizon for it to be visible. Spot The Station will only send out notifications when you will have an opportunity to see the space station, not every time it will be overhead. Do I need a telescope to see the space station? No, you can see the space station with your bare eyes, no equipment required. Can you explain how to identify the space station in the sky?
Did I see the space station last night? The space station looks like an airplane or a very bright star moving across the sky, except it doesn't have flashing lights or change direction. It will also be moving considerably faster than a typical airplane airplanes generally fly at about miles km per hour; the space station flies at 17, miles 28, km per hour.
Can you explain how to read the alert messages? What does all this sighting information mean? How fast is the space station travelling? The ISS circles the Earth every 90 minutes. It travels at about 17, miles 28, km per hour, which gives the crew 16 sunrises and sunsets every day. In the more than 15 years that people have been living onboard, the Station has circumnavigated the Earth tens of thousands of times.
Does the station appear and then disappear because of the light of the Moon? The space station is visible because it is reflecting light from the Sun. This is the same reason that the Moon appears to shine.
Even when the Moon hasn't risen, you'll still be able to see the space station. I haven't received any emails or text messages. What if my city isn't listed? If your specific city or town isn't listed, register using the next closest one. The space station is visible for an approximate 50 mile 80 km radius around each of the listed locations. When are alerts sent out? If you are not receiving the alerts on time, see related FAQs for an explanation. Why am I receiving the alerts hours or even days after sightings?
It orbits the Earth at an average altitude of miles km. Like the ISS, Tianhe is large enough to be readily seen with the unaided eye, though being smaller it is nowhere near as bright. But under optimal conditions, it can become as bright as magnitude Not as bright as Arcturus as it went by, Tianhe rapidly brightened as it then approached the zenith.
As it traversed past Vega, it actually outshone it for a short period. My guess at its brightest it was very near '0 mag. While observing countless passes of the ISS, I always found it to be mostly white. So, viewing Tianhe, I found it most definitely quite a bit different! So, what is the viewing schedule for your particular hometown? You can easily find out by visiting one of three popular web sites:. This site will tell you when and where to sight the ISS.
All you need do is type in your city or town, then click on the map pinpoint to get all the details. You can even sign up to get email or text alerts when the space station is flying over. This site will not only provide you with sighting information for the ISS, but also for Tianhe-1 as well. You must first register and then you can input your location to generate a sighting schedule.
Once you log on this site will automatically provide details based on your IP address Predictions computed a few days ahead of time are usually accurate within a few minutes. However, they can change due to the slow decay of the space station's orbit and periodic re-boosts to higher altitudes. Check frequently for updates. He writes about astronomy for Natural History magazine , the Farmers' Almanac and other publications. Follow us on Twitter Spacedotcom and on Facebook.
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Joe Rao is Space.
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