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  #1  
Old 29-07-2009, 09:46 PM
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Tandum (Robin)
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QHY8 Flats

Can I use flats taken with gain set to 0% on images taken with gain set to 50% ?

I can't get good flats at 50% gain.

Last edited by Tandum; 30-07-2009 at 11:40 AM.
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  #2  
Old 01-08-2009, 05:21 PM
gbeal
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Robin,
Can't answer it for you, but equally can't work out why you can't get them at 50%. Mind you I always shoot at Gain 1 anyway.
Gary
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  #3  
Old 01-08-2009, 07:02 PM
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Tandum (Robin)
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It floods the hystogram at 50%, everything is on the right and the flats don't work. I can't turn exposure time down enough in maxim. Mute point now, tried it already and it works fine
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Old 01-08-2009, 08:48 PM
Alchemy (Clive)
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i use mine at 50 gain and 117 offset.
if the flats and lights dont match, it , in my experience is a dud. you need to calibrate it properly so the offset and the gain are correct.
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Old 02-08-2009, 01:21 AM
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Tandum (Robin)
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It looks like it's only an issue with the tak @ F5.9, flats out of the vixen @ F9 worked tonight. Might be easier to run gain 1 when using the tak and reducer cos last thing I wanted to do was modify the light box.
Having 2 imaging scopes is quickly becoming a pain in the rear.

[edit]
I suppose I should add that I get offset 130 with gain 0% and offset 120 with gain 50% but bias files for both are very similar. I guess the rub is that the bias files come off the flats as well as the lights.

Last edited by Tandum; 02-08-2009 at 04:13 AM.
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  #6  
Old 03-08-2009, 01:24 PM
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h0ughy (David)
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Quote:
Originally Posted by Alchemy View Post
i use mine at 50 gain and 117 offset.
if the flats and lights dont match, it , in my experience is a dud. you need to calibrate it properly so the offset and the gain are correct.
so how do you do that?
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  #7  
Old 03-08-2009, 03:40 PM
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Tandum (Robin)
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Here's a quick guide on setting the gain and offset.

http://www.lightstorm.at/pdfs/QHY8_settings.pdf
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Old 03-08-2009, 05:34 PM
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h0ughy (David)
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thanks Robin
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  #9  
Old 03-08-2009, 09:10 PM
Hagar (Doug)
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Hi Robin,
The offset and gain settings for flats really wont matter too much. You are really only imaging imperfections in the imaging train and will use this file to remove them off the final image. Most software packages do a fair amount of work to the image to make a final master flat. The important things to remember are that the focus, camera alignment have not been changed between taking the lights and the flats. You may also find that a set of bias frames taken at the same settings as your lights will correctly calibrate the master flat for you and make application of the flats very effective.

Welcome onboard with a QHY8 David. (Houghy) You will love it.
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  #10  
Old 03-08-2009, 09:37 PM
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h0ughy (David)
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Quote:
Originally Posted by Hagar View Post
Hi Robin,
The offset and gain settings for flats really wont matter too much. You are really only imaging imperfections in the imaging train and will use this file to remove them off the final image. Most software packages do a fair amount of work to the image to make a final master flat. The important things to remember are that the focus, camera alignment have not been changed between taking the lights and the flats. You may also find that a set of bias frames taken at the same settings as your lights will correctly calibrate the master flat for you and make application of the flats very effective.

Welcome onboard with a QHY8 David. (Houghy) You will love it.
thanks Doug
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  #11  
Old 03-08-2009, 10:03 PM
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Tandum (Robin)
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Cheers doug, I figured it was pretty much the same as ISO with a canon and I guess so long as the bias shot is similar it won't really matter. Once the moon moves on I'll have a closer look but I think I'll find a gain of 50% @ F9 and gain 0% @ F6 will work for me and that should give me good flats as well.
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