In Camera Dark Reduction - Hot pixels or star colour?

[DJT (David)]

Hi
Wondering if someone can help

The image below is a very tight crop of NGC 5189 (Dunlops Best). The image was shot on the night of the full moon (how corny does that sound) so didnt expect much but on processing today I was reasonably happy. A bit noisey and I need better data but...My question though is are the star colours rights or am I happily processing hot pixels?

http://i1154.photobucket.com/albums/...rocessedV2.png

This is basically 6 subs of 1200 seconds at ISO 400 with in camera darks using a Canon 30d and a CLS clip in filter on a SWED100. Stretched in CS6.

I like In camera darks because you are doing reduction at approximately the same temperature as the light, but if they are not effective then I wil l have to move to taking seperate darks.



Any suggestions??

[irwjager (Ivo)]

Hi David,

You should be able to distinguish hot pixels in the non-debayered frames. They stand out like the proverbial canine testicles They'll look like single bright/white pixels.
However, when they get debayered their erroneous data, depending on the debayering algorithm chosen, 'bleeds' into the neighboring pixels, making them look much more like stars.
I can see one ore two definite hot pixels in there, but not sure about the others.
Another thing you can (should!) do is 'dither', shifting the image slightly between subs, so hot pixels get 'spread' over the image, making it easier for the stacking algorithm to pick out and eliminate.

Hope this helps!

Ivo

[DJT (David)]

thanks Ivo, very much appreciated