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Saturday, January 21, 2006

 

Orion again


From Left to right, Orion, stack of 5x6 seond exposures; Orion, single six second exposure; Star Map of Orion for comparison. As usual, click on the images to see a full sized version.
Thanks to Megan, who suggested stacking exposures to increase sensitivity, I went out last night to try it out. The resuklts you can see above. I took 5x six second exposures on my Olympus muj:300 (in night mode with flash off and super high quality resolution) and stacked them in iPhoto4. This is suboptimal as iPhoto doesn't have a real stacking mode, I used stich at 50% transparency instead (must get PaintshopPro 9). I then adjusted gamma to an outrageous 2.33, and adjusted brightness up by 10 (so you can actually see it in the thumbnails).

Anyway, with just 6 images stacked, the results weren't markedly better than the single shot (see the right hand image for comparison). One thing stands out, I have a major hot pixel problem. This is probably exacerbated by the fact it was blinking hot last night, so the hot pixels showed up more. So I really need a dark frame. I should do this again with a) a drak frame, b) a cool camera c) using real stacking software. (any other hints gratefully accepted)

Comments:
The random noise is definitely lower in the stacked image, but a dark frame would help a great deal!
 
Actually, you could try stacking in the gimp (www.gimp.org) using the "screen" mode, it can work quite well (and it's free).
 
If you use Windows to process your pics, there is a free tool called "Black-Frame NR". Here's the URL:
http://www.mediachance.com/digicam/blackframe.htm
Nice photos!
 
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