Bad Pixel Map

[martin_h]

As a follow on to the "How Many Darks?" thread I have been experimenting with bad pixel mapping, as per Ollies lead and have come up with the following results..

1. A bad pixel map made from a stack (20) of 3 mins darks and applied to a kappa sigma stack of 20 x 3 min lights - result - no hot pixels in the resulting image.

2 A bad pixel map made from a single 3 min dark frame and applied as above... result - no hot pixels in the resulting image.

3 A bad pixel map made from a single 3 min dark frame and applied to a kappa sigma stack of 20 x 15 mins lights - result - no hot pixels in the resulting stack.

Conclusion: 1 size bad pixel map fits all light frames regardless of their exposure time, and you only need 1 dark to produce the map.

Now this is only an afternoons worth of testing and all results were only checked by eye on a 200% zoomed image, but, I was testing on images captured with a Kodak KAF8300 one shot colour CCD and if you have ever seen a dark frame from one of these you'll know that it looks like a snow storm at midnight!