Astronomy blog

How To View International Space Station Passes

By travel
7/13/2010, 7:50:05 AM

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Hello, astro-nuts!

The past couple of weeks have been great for viewing the International Space Station, either because of clear skies or because of its angle of flight in orbit. For those of you who have yet to see it and don't know what to look for, here is some information.


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The ISS-NASA

First, you need to know whether the space station will be flying over your location on a given day. Contrary to what many might think, the ISS does NOT fly over the same locations every day, and the exact times change. It can take a different path and misses an area completely; other days it might fly over during daylight hours, so you can't see it. There are several good websites you can check out that will tell you when the space station will be over your location. Thanks to our Facebook fans who responded to Alex's (A-Sos) post about viewing the ISS.

*Heavens-Above, my personal favorite. Allows you to enter your exact location and get visible passes for the next several days. You can even go back in time and see previous passes. Information includes magnitude, direction, height, and a star map so you know exactly where to look.

*NASA Satellite Sighting page-click on your state and then choose among the city list either the place you live or the town closest to it (the times won't vary that much). If you want to enter your exact location, there is a nice Applet you can use to get your exact location by zipcode or lat/lon.

*Spaceweather Simple Satellite Tracker-simple is right! All you do is enter your zipcode and it will produce a list of passes for the next couple of days; and you can choose which objects you want to look for.

Most of the time, the pass information includes the time, direction, altitude and magnitude**. For magnitude, a negative number means an object will be brighter. If its a positive number, it'll be dimmer. For perspective on brightness, Venus shines at close to magnitude -4 at its best. The limit of our naked eyes at dark rural sites is around +6. In urban or suburban locations, it may be more like +3.

As far as altitude goes, if you stretch out your arm and make a fist, your fist covers about ten degrees. Ninety degrees is directly overhead.

Usually, if a pass will be bright, its a little longer too. Some passes, when the ISS is dimmer, are a minute or two, if that. The brighter passes can last 4-5 minutes, or longer depending on how obstructed your view might be. It's also important to know your directions--you don't want to be looking in the wrong direction or you might miss the pass entirely!

**You may also see "azimuth", which is just another way of expressing the cardinal directions (N,E,S,W), but it uses degrees instead of the actual direction. North is zero, east is 90, south is 180, and west is 270.

Once you know when and where the ISS will make its pass, you'll need to know what to look for! A few important tips:

*The ISS will NOT blink or have multi-colored lights (Don't mistake a plane for the ISS).

*The ISS will be visible longer than a second or two, and will NOT have a smoke trail behind it (that would be a meteor).

*The ISS will resemble a moving star, usually a white or yellow-ish color, and may fade or get brighter as it passes.

*Unless you're really experienced with tracking telescopes, astrophotography, etc, trying to use an instrument other than your naked eye to follow the ISS as it passes may be an exercise in frustration (I have heard that binoculars might be easier but...). It moves much too fast to easily keep it in a telescope's or telephoto lens' field of view. If you want to try your hand at photographing the station (or meteors), check out these tips.

*There aren't many shuttle missions left, but pay attention to dates when the shuttles are expected to dock at the station...you can see the two close together near docking and undocking times. The station also gets brighter when the shuttle is docked there!


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The ISS in 2008, through a 10-inch Newtonian Telescope-Ralf Vandebergh

Keep your eyes to the sky and enjoy the view (of the space station!)! ~Lisa C.

The views expressed are those of the author and not necessarily those of AccuWeather, Inc. or AccuWeather.com

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