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 Post Posted: Mon Oct 23, 2017 1:25 pm 
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Joined: Tue Jul 25, 2017 8:23 pm
Posts: 6
Hello everyone here,

I've got the Color 178 Camera, cooled and I'm making some progress with it (this is my first serious venture into CCD asttrophotography) and I have this thing happening in the upper right corner and across the bottom of all my images, regardless of where they were taken.

You can see the glow from the upper right corner that starts to show up as you do your level stretching and all that. And a strange mottling across the bottom with a glow in the lower right.
The only preprocessing I've done is remove bad pixels since I don't really understand the whole bias current thing yet, Could that be what I'm facing here? Is there a way to do that after the fact?

For this image (NGC 253) the cooling was on (-30°C) and it is 17 one minute exposures were stacked in Nebulosity 4, processed there and then more in photoshop. This issue is preventing me from recovering the lower right portion of the galaxy and I'm hoping there's some bit of knowledge out there I don't know that will help.
Any ideas?
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 Post Posted: Mon Oct 23, 2017 5:35 pm 
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Joined: Mon Aug 01, 2016 3:51 pm
Posts: 102
That's amp glow.
Start taking dark frames and bias - problem solved.
Also start taking flats too.


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 Post Posted: Mon Oct 23, 2017 5:51 pm 
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Joined: Sat Jul 29, 2017 1:03 pm
Posts: 10
What you are seeing is a combination of amp glow and vignetting. If you recorded your camera settings and temperature, SharpCap does this for you then you can go back and take the needed dark frames then subtract them from your light images. Flat frames are a different matter. You need the camera in and telescope in the exact optical arrangement you used to take your images. Temp is not relevant here. You just record uniform illumination such that the histogram is centered. Autostakkert can handle dark and flat frame subtraction for you. There's a good chance you can get descent picture with just the dark frames if you were in fairly dark skies.


Bill the Sky Guy wrote:
Hello everyone here,

I've got the Color 178 Camera, cooled and I'm making some progress with it (this is my first serious venture into CCD asttrophotography) and I have this thing happening in the upper right corner and across the bottom of all my images, regardless of where they were taken.

You can see the glow from the upper right corner that starts to show up as you do your level stretching and all that. And a strange mottling across the bottom with a glow in the lower right.
The only preprocessing I've done is remove bad pixels since I don't really understand the whole bias current thing yet, Could that be what I'm facing here? Is there a way to do that after the fact?

For this image (NGC 253) the cooling was on (-30°C) and it is 17 one minute exposures were stacked in Nebulosity 4, processed there and then more in photoshop. This issue is preventing me from recovering the lower right portion of the galaxy and I'm hoping there's some bit of knowledge out there I don't know that will help.
Any ideas?


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 Post Posted: Tue Oct 31, 2017 2:52 pm 
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Joined: Tue Jul 25, 2017 8:23 pm
Posts: 6
Ok Guys, thank you so much!

I use Nebulosity 4 as my capture program (I'm Mac based). It's got some good documentation about how to deal with bias, darks and all that. I'll start incorporating that into my workflow.

I'm really impressed with what others have been able to do with this camera, I need to be able to do similarly well so thanks again... I'll see what I can do with this image!

Bill


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