Astroblog: What, Orion again?

Wednesday, January 25, 2006

What, Orion again?

The skies are brassy with smoke from the kangaroo Island fires, it's going to be 39 degress tomorrow, so we are off camping. I'll leave you with yet another picture of Orion, stached as suggested by Megan using Gimp. It's interesting :-)

# posted by Ian Musgrave @ 5:30 pm

Comments:

Nice image Ian. Were you tracking with your camera? If you weren't I suspect that the strange dot patterns are actually hot pixels. Although the hot pixels stay in the same position on the camera image, when you align all the images using the stars, the hot pixels will appear to move. The dotted appearance results from the times when you weren't exposing. Of course, I could be totally wrong but it is consistent across the whole image. Subtracting a dark frame from each image before stacking should make quite a bit of difference.

# posted by

Anonymous : 9:31 am

G'Day Stuart, no I wasn't tracking, and yes they are hot pixels (see the Orion post further down). I was using Megans suggest Screen mode in The Gimp to stack the images, and the hot pixels come through, but it's a very pretty effect though). I don't know how to subtract a dark frame in the Gimp (Megan, any clues?). I can do it in Registax, but registax took over an hour of thrashing to stack these images, so I'm not sanguine about using it. Anyway, I have some more images to stack, so I'll experiment some more.

# posted by