QHY8 Flats

[Tandum]

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.

[gbeal]

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

[Tandum]

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 :)

[Alchemy]

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.

[Tandum]

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.

[h0ughy]

so how do you do that?

[Tandum]

Here's a quick guide on setting the gain and offset.

http://www.lightstorm.at/pdfs/QHY8_settings.pdf

[h0ughy]

thanks Robin

[Hagar]

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.

[h0ughy]

thanks Doug

[Tandum]

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.