Tuesday, September 14, 2010

It's a Bird, It's a Plane...

Occasionally I keep a watch on Heavens-above.com for good passes of the International Space Station (ISS) or for Iridium Flares. Seen from a dark sky, they can be quite spectacular, but even from town they are fun to hunt out.

I noticed a few days ago that the ISS would make a good pass over Southern Arizona tonight. Starting at 7:36pm in the NW, it would spend 4 minutes crossing the sky until entering the earth's shadow in the SE. I've tried to image it, but it always seems disappointing. Tonight I had planned to do it from Kitt Peak while visiting a friend observing on the 90" telescope, but between my cold and Melinda's call to come in to work tonight, I thought I'd try it from town again.

The 8mm fisheye lens that the club has on long-term loan has an ultra-wide field of view, so used it on my Canon XSi. In test exposures shortly before the ISS appearance, skyglow in town dictated that I drop the ISO to 200, and f-stop to F/4 to keep from saturating the detector in a 4 minute exposure. The 5-day-old moon got hidden behind my neighbor's palm tree. Right on schedule, it appeared below the Big Dipper and swiftly crossed the sky, much brighter than Jupiter low in the SE. I always think there should be a sound associated with it, like that of an airplane, but no, dead silence... It made it to 75 degrees high, nearly overhead. In the photo the summer triangle is visible overhead, a distorted view of the Big Dipper at lower right, Cassiopeia upper right. I got lazy on processing, and used Photoshop's "auto color correction", thus losing the peach-colored glow of local light pollution. There are a few ghost images of bright lights on my neighbors' houses.

These days, amateurs are not content just to watch the passes, but image the ISS through telescopes equipped with webcams or video cameras. Surprisingly good results can be obtained, though I've not tried it (yet!). There are also programs to allow you to catch it crossing the face of the sun or moon! Fun stuff!

1 comment:

David A. Harvey said...

nice! Watched it from KP - wish you had been here - right over the top of us!