Finding and Observing the International Space Station

If you are interested in seeing more than just the moon, stars and planets in the sky, the International Space Station is a good object to search for. It is bright enough to be easily seen with the naked eye, and its location in the sky can easily be found using some tools available on the internet.

The International Space Station (ISS), started its journey with the launch of its first module, Zarya, on Nov. 20, 1998, and has been orbiting Earth ever since. It can easily be seen from Earth without a telescope as it orbits overhead. However, because on each pass overhead it traverses the sky in only a few minutes and its orbit only passes above the horizon of a given location a limited number of times per day, knowing when and where to look is important if you want to see it. Additionally, for it to be visible, sunlight needs to be reflecting off its surface, so it is only visible for a short time before sunrise and a short time after sunset.

Fortunately, there are a few tools available to you that will help you to know when and where to look for the ISS at your location. NASA has a web-based tool that will give you a listing of the times when it will be visible from your local area, as well as the location in the sky where the ISS will first appear and where it will last be visible on that pass. Go to NASA's Human Space Flight page here and navigate to your location under the “Sighting Opportunities” on the left side of the page. Additionally, on NASA's HSF page, you can load a Java Applet, called Skywatch, that shows the orbital path of the ISS. Skywatch can also be used to calculate the precise times that the ISS will be visible at your exact location, if you are not located near one of the cities that can be found in the Sighting Opportunities listings. The data provided by NASA's tools will appear in the following format:

Satellite Local Date/Time Duration Max Elev Approach Departure (MIN) (DEG) (DEG-DIR) (DEG-DIR)

ISS Sat Apr 07/04:21 AM 1 18 18 above ENE 10 above E

“Satellite” refers to which satellite is being viewed, because other satellites in addition to the ISS are listed when they are visible.

“Local Date/Time” tells you when the satellite will first be visible on a given overhead pass.

“Duration” is how long the satellite will be visible.

“Max Elev” is the highest angle above the horizon where the satellite will be visible. It is in degrees, with the horizon being 0 and 90 being directly overhead.

“Approach” is the location where the satellite will first be visible. This is given as the number of degrees above the horizon and the direction to look from your location.

“Departure” is the location where the satellite will last be visible and is given in the same format as the Approach.

Additionally, I like to use Stellarium software, which I discussed in my last guest blog post here. In Stellarium, you can load a satellite plug-in that will display satellites in addition to the stars. By using the data from NASA and displaying what the sky will look like at your location at the time the ISS will first appear on a specific pass, you will be able to see where the ISS will appear among the stars. This will make it much easier to identify precisely where in the sky you will be able to see the ISS by having some stars to use as a reference.

Although I haven't used binoculars to look at the ISS yet, I understand that when conditions are right, with binoculars you can see some of the shape and structure of the ISS, rather than just a moving point of light.

For additional information on the ISS, you can go to the NASA ISS page here and subscribe to the ISS Facebook page here.

Happy Stargazing!

- Guest blogger and amateur stargazer, Paul Adomshick

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