Astroblog: Orion again

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)

# posted by Ian Musgrave @ 10:04 am

Comments:

The random noise is definitely lower in the stacked image, but a dark frame would help a great deal!

# posted by

Anonymous : 4:47 am

Actually, you could try stacking in the gimp (www.gimp.org) using the "screen" mode, it can work quite well (and it's free).

# posted by

Anonymous : 4:50 am

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!

# posted by

Anonymous : 12:36 am