Dither \ Darks \ Flats

[AlistairW]

Hello,

Just wanted to check, if you use dithering, you still should take darks and flats right ?

Thanks

Alistair

[johnrt]

You will still need flats most certainly as they correct uneven illumination and calibrate out dust particles. You will also need bias. As for darks, that's a maybe, try it with and without and see what you get. Theoretically you shouldn't, but the practise doesn't often agree with the theory.

[ollypenrice]

With a set point cooled camera darks or a bad pixel map might help but might not. With an uncooled DSLR they are very likely to do more harm than good because of being at unpredictable temperatures. So I agree with John.

Flats are always an enormous help (when you get them right! Use a master bias as a dark for your flats. This is important.)

With a DSLR a large dither can reduce background sky colour mottle according to Tony Hallas. He suggests a 12 pixel dither. This is far higher than the dither you'd use for CCD.

Olly

[AlistairW]

Interesting. My DSLR has been modified to have set point cooling. So it's not a problem to take the darks whenever and build a library. I have often wondered if a bad pixel map might be a "better" way to go. But I am unsue of how to relate this to dither. I need to read up more I expect, but my instinct says that even if you use dither the stack much realign the images, so the use of a master dark would help ???