Tuesday, June 26, 2012

ISS Jumps Over The Moon

Click on the Image to see a larger image

The local weatherman mentioned that the International Space Station was going to pass across the face of the Moon tonight.  So I checked the one source that is easy to use for getting this type of information: heavens-above.com.  It told me that the ISS was going to pass north of the Moon from my location, about 30 miles south of Kansas City.  Putting in some locations further north, it looked like some people north of Kansas City might see it cross the Moon, but not me.

I decided to take some pictures of it anyway, so I set up my Canon Xti on a tripod, attaching my 10-22mm wide angle lens on it.  I auto focused on the Moon, then turned off auto-focus.  I took a few test exposures to find out the best one to use.  The ISS took about 5 minutes to go across the sky, rising in the West and fading into Earth's shadow in the South.  One minute exposure at f/3.5 and 1600 ISO was way too bright, making the scene look like daylight.  A 5 minute exposure would turn the image white.  Lowering the ISO and/or increasing the f/ratio would make the sky darker, but it would also dim the stars and the ISS, so  I settled on 15 seconds at f/3.5 and ISO 800.

It took 14 images to get it as it cleared the tree tops until about 3.5 minutes later when it faded into the Earth's shadow.  I processed the 14 images in a free program called DeepSkyStacker, which stacked all of the images on top of each other and produced one image.  Images created this way make a RAW file, which is very dark, so I had to put it into Photoshop to stretch it into the image you see above.  If you look close, there is a small gap along the track of the ISS , this is caused by the small amount of time between each exposure.  The shorter streaks are of course stars trailing because of the long combined exposures.

It turns out that a friend of mine, Joe Wright, who lives way north of Kansas City, said it did go across the Moon where he lives.  He tried to take pictures of it, but says his camera failed.  Better luck next time Joe.

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