Subtracting dark frames

[EzyStyles (Eric)]

Hi guys,

I was wondering if i am doing this correct.

1: Do you stack your images first then stack your darks and with the 2 stacked files, you subtract one from another?

or

2: do you subtract your stacked darks for each individual frames then stack again once this is done?

I hope i made sense

Thanks.

[Striker (Tony)]

Number 2 is correct.

[EzyStyles (Eric)]

cheers Tony. I believe that also applies for flats?

[Phil]

yep no:2 average you darks then subtract that master dark with each of your images. Try to get your darks as close to your images as time and temp. This will help to. Its one of those things we all hate to do but we have to to get good images.
Good luck Also if you average you darks use at leased 3 or more.
Phil

[EzyStyles (Eric)]

thanks phil cheers. I normally avg 5 or more dark frames. I guess the more the better.

[Geoff45 (Geoff)]

The other (ie slack) way is not to think about it at all. Just select lights, darks, bias, flats, flat darks and let the automatic image processing button in something like ImagesPlus do it for you.
Geoff

[Carl]

Hi Eric

I have been advised that the correct process is No2: Subtract your darks for each individual frames then stack once this is done.
If you are stacking with Deepskystacker or DSLRmax or similar the process is Creation of master dark frames, followed by subtraction of dark frames and or automatic calibration, registration of images then stacking.
If you are stacking in Photoshop, subtract your dark frame from each individual light frame then stack.

Regards
Carl