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Author Topic: darks flats and bias frames  (Read 36 times)

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Offline andy@amkat.co.uk

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darks flats and bias frames
« on: 13:34:05, 13 August, 2018 »
Hi all after looking on the interweb i am still confused re calibration frames
some say don't use bias and flats some say do and visa versa
some say you have to take dark's the same time you take lights
as for flats some say a light box is best or a white t shirt

can i just take flats and make a folder of them along with dark's  i was thinking if i mark the camera and the scope so as to line both up for every session would that work ???

i have ordered a book every photon count hope it helps
 
All the best Andy
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Offline Einari

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Re: darks flats and bias frames
« Reply #1 on: 17:19:04, 13 August, 2018 »
Depends on the camera.
It it's DSLR (or astro camera with no sset point cooling) then taking darks can be difficult as darks should be taken at same temperature as lights.
That's why some leave darks out as they can introduce more noise so not good.
But when you have set point cooling in camera you can set a fixed temperature for camera so they match.
I do flats with flat box (or with EL panel). I do know that some swear by t shirt and sky flat method.
If it works then I guess both are fine.
You can make a dark library yes - if you can make it 'temperature organized', ie a folder for each camera temperature.
But flats are bit more demanding - even if you can make camera exactly same orientation each time and use exactly same focus each time you still have a chance that dust motes (which you are trying to eliminate with flats) are moving so flats no more are working.
So the common wisdom is to take flats after (or before) each imaging session.
Hope this makes things bit more sensible.
Tapio

Celestron C8, C9.25" & Hyperstar, iOptron CEM60-EC, TS 80 triplet,  Coronado PST, SXV-694,  ASI120MM/ASI174MC Cool

 

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