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Treebeard's Stumper
11 January 2002

Winter Stars

DMS students have my assignment to go outside at night this week and count how many stars they can see in the "bowtie" of the constellation of Orion. It's been cloudy, but I hope it clears for the dark new moon this weekend. Look southeast after sunset and view the bright planets Jupiter and Saturn flanking mighty Orion, along with the Milky Way and many other brilliant stars and constellations nearby. Summer nights are more comfortable for stargazing, but why does the winter night sky seem so much more dramatic? (I can think of several different reasons!)

I took this picture of Orion during the great Leonid Meteor shower on November 18, 2001. I set up my Olympus 2040Z digital camera on a tripod pointed at Orion, with manual exposure set to the max of f/1.8 @ 16 seconds, hoping to catch something. I took over 100 photos, and I was lucky to get this one keeper.

Note there are two parallel meteor streaks in the original photo. Look for the faint one about half-way up Orions upper-left torso. It's easier to see in the enhanced negative image (middle below). There are better Leonid pictures here.

Digital camera CCD ("charge-coupled device") sensors get "hot pixels" during long exposures. Serious digital astro-photography fans use special CCD sensors and keep them near freezing to minimize digital noise during long exposures. That's not recommended with a commercial digital camera! My original photo was speckled with red, green, and blue hot pixels (left). I used the freeware HotPixel Eliminator program and then used Paint Shop Pro to fiddle with contrast and gamma and histograms to make a "clean" image. But I'm pretty sure some of those "stars" are just enhanced hot pixels that got by the filters. I'll use the freeware star chart program Cartes du Ciel (right) to make sure.

My school assignment is to:

  • Find Orion at about 8:00 P.M. using the January star chart from SkyMaps.com;
  • Sketch what you see;
  • Count the stars within the "bowtie" of the main body of Orion; and
  • Try reading a simple "Distance Visual Acuity (E Game)" eye chart (in the dark) that I found on the Web.
Of course city lights will make a difference. That's the point. I'll report our results in my answer. It would be more difficult to do this assignment in the summer. Why is the winter night sky so much more dramatic?

Answer


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Copyright © 2002 by Marc Kummel / mkummel@rain.org