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nobbygon
member
Reged: 03/20/09
Posts: 75
Loc: Australia
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Hi, Im fairly new at AP and I was wondering If anyonw knew of a good tutorial or web page that would explain how to take and use these different frames. (I know how to do darks, but thats it). I would assume it would take too long to explain it on here. I use a DSI II Pro if that has any difference.
Thanks in advance
Cheers, Angus
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Sidereus Nuncius
super member
Reged: 03/27/05
Posts: 175
Loc: Chester County, PA
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There is a "how-to" on the Deep Sky Stacker web site.
A flat frame can be captured using various techniques:
- taking a picture of the twilight sky (t-shirt flats)
- using a "light box"
- et cetera
Essentially, you want to take a picture of any evenly-illuminated light source. Take your flats with your camera and focuser in the same position used when capturing your light frames.
Bias frames are simple to create: take the shortest possible exposure with the shutter closed (or the lens cover on). AFAIK bias frames are only used to "scale" dark frames.
Also, check out this thread
I'm sure there are others accessible via the "Search" function.
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Regards,
Louis Marchesi
TMB 152, WO ZSFD80 Anniversary
AP 1200GTO
SBIG ST-2000XM, CFW9, Astrodon LRGB
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HunterofPhotons
sage
Reged: 04/26/08
Posts: 266
Loc: Rhode Island, USA
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Quote:
.... AFAIK bias frames are only used to "scale" dark frames....
A flat needs to have a bias subtracted to work properly.
dan
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gavinm
scholastic sledgehammer
Reged: 08/26/05
Posts: 807
Loc: Auckland New Zealand
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Quote:
Quote:
.... AFAIK bias frames are only used to "scale" dark frames....
A flat needs to have a bias subtracted to work properly.
dan
A flat needs to have a dark subtracted to work properly, and that dark contains the bias.
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Gavin
Mt Albert Grammar School Observatory
Auckland, New Zealand
http://www.mags.school.nz/astronomy/index.html
12" LX200R F6.8 AP
SBIG ST7-XME + CFW10
Moonlite SCT focuser w/ temp
Skywatcher Equinox ED80 Pro (ADM dovetail)
+ other stuff
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HunterofPhotons
sage
Reged: 04/26/08
Posts: 266
Loc: Rhode Island, USA
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Quote:
Quote:
A flat needs to have a bias subtracted to work properly.
dan
A flat needs to have a dark subtracted to work properly, and that dark contains the bias.
Hi Gavin,
There are a couple of considerations to take into account.
Theoretically, you would subtract a dark, but in actual practice the high ADU count of a flat means that it has a strong S/N.
The short duration of the dark for the flat means a high uncertainty or 'noise' for the dark, even if you're taking 30-40 flat darks. Subtracting this dark will add noise to the flat.
The build-up of dark current is minimal for a short duration flat dark. In practice, subtracting just a well constructed bias master from a flat results in a cleaner master flat.
dan
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nobbygon
member
Reged: 03/20/09
Posts: 75
Loc: Australia
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Thanks for the help everyone. I'm pretty sure I know why and how to take all of these frames now. Anyone know of a good tutorial that shows you how to apply these frames in Maxim Dl 5?
Cheers, Angus
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