Calibration frames for LRGB and Narrowband

[Hughsie]

I understand that for each LRGB or Narrowband filter I will have to take flat frames for each one, but with regard to dark frames do you need to take darks for each filter?

Apologies for what may appear to be a daft question but any guidance would be appreciated.

 

John

[Freddie]

No need for darks for each filter (no light is coming through so it doesn’t matter which filter is there) Darks only need to match temp and exposure.

[MarsG76]

2 minutes ago, Freddie said:

No need for darks for each filter (no light is coming through so it doesn’t matter which filter is there) Darks only need to match temp and exposure.

+1

 

[Hughsie]

Thanks to you both, I thought that was the case.

 

J

[red dwalf]

i would take camera off the setup completely to take dark's and put it somewhere completely dark, it`s amazing how some light can get into an imaging train, then make a little library of your usual expose times, i.e. 1 minute, 3 minutes, 5 minutes and so on at your usual imaging temperature, mine being -10 degrees Celsius, these dark's will keep for a good 5 or 6 months before they need doing again.

[ollypenrice]

Orthodoxy says you need flats for each filter but my experience of practice says that usually you don't. You might get a dust particle on one filter which is different from the other filters but I'd say I have this about once every five years at most. Besides, these dust motes are a long way from the chip and well out of focus. Most bunnies come from much nearer the chip - the chip window, for instance. And if we are talking about LRGB, think it through. Just take a luminance flat. it might be slightly imperfect when applied to R, G and B but then the resultant RGB image will itself be illuminated according to the perfectly flattened luminance layer. Shoot flats per filter if it scratches your OCD itch but don't do it because it is likely to influence the final image. I don't believe it will. I only do 'flats per filter' when my collaborators insist upon it. 

Olly