The Half-Astrophysicist Blog

ISS Passes This Week

The International Space Station is in the middle of a good series of passes for the U.S.  Check out times for your location at sites such as Heavens Above or use Space Weather’s Simple Satellite Tracker.

The ISS is very bright and easy to see.  Take special note of its color as it is reflected sunlight.  Since all satellites are illuminated by reflected sunlight, they all have about the same color. If you see something else in the sky moving steadily with about the same color as the ISS, you probably are seeing another satellite.

Near the solstice we get more good ISS passes.  This is due to a combination of factors.  First, the ISS is in an orbit which is inclined about 57 degrees to the equator meaning it spends more time farther north (and south) of Earth’s equator.  Second, the Sun is also farther north at this time of year which means it can illuminate the station better after sunset and before sunrise.  Twilight lasts longer the farther north you go, so people in the northern U.S. can get two good passes in an evening (here in Arizona, twilight doesn’t last as long so we usually get only one good pass per night).  Go to a weather site and check sunset times and the length of twilight at different latitudes.  It can be illuminating to say the least.

I thought about getting an ISS photo last night, but it was passing very close to the Moon from where I live.  To get the ISS, I would have used too long of an exposure and the Moon would blast everything away.  There are some good passes I can try this week.

If you want to photograph the ISS, you need a camera that can do timed exposures.  Simply point the camera near the ISS, open the shutter for 10-20 seconds, and you should get a streak on the image.  You can change the ISO of the film depending on the lighting conditions.  If the sky is very dark, you might try 800. If it is still somewhat light, use lower ISOs so you don’t overexpose the sky.  The passes can last 3-4 minutes, so you can try multiple exposures if you are quick!

July 6, 2009 - Posted by | NASA, Observing

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