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Old 01-09-2014, 07:51 PM
Tony_ (Tony)
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Image banding

G'day,

Does anyone know what causes this banding/streaking in images? (and how to get rid of it).
Cenralds cooled 60d. about 60 x 45 secs. ISO 1000. IDAS LPS filter.
(+flats, darks and bias).
Ambient temp = 8C, Camera Temp = -15C.
Images taken as JPEG and converted to 16 bit TIFF. (I know I should take RAWs).
The image I took just before this one had a little banding - but nowhere near as much as this one.
I thought it may be noise related but it doesn't happen every time. I seem to get it on images of fairly sparse areas like this one. The temperature was low enough - I wouldn't expect noise to be that much of a problem?
Also, despite the low subs and overall time, the image seems particularly faint. Is it caused by DSS? I often take 40 - 60 minute total exposure time and I get better images than this. (I also occasionally used to get this type of banding with my 550d which isn't cooled).
(Don't worry about the star shapes etc. - that's another issue).

Any suggestions appreciated.

Regards,
Tony.
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  #2  
Old 02-09-2014, 08:14 AM
SteveInNZ
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Is this unguided ?
I get (and expect) this when I stack lots of unguided 30 second subs.

Steve.
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Old 02-09-2014, 01:02 PM
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BlackWidow (Mardy)
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Very interesting Tony.. I did some imaging the other night using a QHY8 and got the same thing. A friend of mine said it may be that the cooling in my camera was not working. I was Guided using PHD, and seemed to be getting good guiding. I am in the same boat that I don't know why. Makes it hard to fix the problem. Is it the stacking software causing it?
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Old 02-09-2014, 05:07 PM
Tony_ (Tony)
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It was guided - I am having some problems with guiding, hence the short subs. I'll try to work that out next. I've been getting double stars and elongated stars - I think I may have the balance too good.

The banding is also in the subs - so it is a capture issue of some sort, hopefully not a camera problem. The camera has a built in temperature gauge that was at -15C, but even without cooling I wouldn't expect this level of noise when it is only 8C.
I don't know why but also with my 550D I seem to get banding occasionally when I try to image fainter galaxies in sparse fields. I never get this banding with brighter objects in richer fields. I don't know why?
Also strange, in the past I have used ISO up to 6400 and I don't get this sort of noise/banding (if that's what it is). I'll see how I go next time - hopefully it will be okay.
Last week I imaged at ISO 1600 and didn't get banding, this time I dropped to 1000 - which should have less noise?
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Old 03-09-2014, 11:02 PM
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JB80 (Jarrod)
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I get similar banding in my dslr and the two things that I have seen that make sense is that the darks are at a different temp than the light and you should use dithering.
For me I think it is the temp that is the culprit as if it was dithering it would happen all the time and it doesn't, plus I can get lazy with my darks.

As for a CCD I can't say.
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