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issue with my stack

Optolong L-eXtreme Acquisition Deep Sky Artifacts Help Needed
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Renaat Vandewiele avatar
Renaat Vandewiele avatar
Hi,

I have an issue with my stack. the green red circle in the image (only 3hrs of data) without a filter. I keep wondering where this comes from. anybody an idea?
on the right a stretched image of my master flat. If I use a optolong l-extreme I don't get these artifacts. could this be a lack of uv/ir cut filter? it should be in my camera Altair hypercam 294c protec.
thank you for a reply
toygar_113 avatar
toygar_113 avatar
I have same issue with QHY 294C Pro. I only get them with UV/IR cut filter of without filter but not with narrowband filters, I even tried with 7nm SII and it did not produce these patterns. I tried 2 different scopes, with or w/o coma corrector/field flattener, UV/IR cut filter before and after coma corrector, different methods for taking flats and different exposure times and 2 different UV/IR cut filter. So I guess it is about the camera, maybe bad coating on window?

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Lynn K avatar
Lynn K avatar
They are dust donuts.  The dual- band filter has different/less dust.  It also created a darker background,  so the dust donuts are less evident.  You need flat calibration. Any camer filter combination with dust will create these effects. 

Lynn k.
Tom Marsala avatar
Tom Marsala avatar
It looks like you're shooting from a bortle seven or eight sky. Besides the dust motes that you see there, that green and red is classic gradient from light pollution. You didn't say whether or not you're using flat calibration, but we definitely need to use flats! If you stretch aggressively that's what light pollution gradient stacks will look like.
Tom
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Brian Diaz avatar
Brian Diaz avatar
Renaat Vandewiele:
Hi,

I have an issue with my stack. the green red circle in the image (only 3hrs of data) without a filter. I keep wondering where this comes from. anybody an idea?
on the right a stretched image of my master flat. If I use a optolong l-extreme I don't get these artifacts. could this be a lack of uv/ir cut filter? it should be in my camera Altair hypercam 294c protec.
thank you for a replyhi 

i used for long time a zw0 294mc pro 
it is a  294 mc pro classic  pattern
 try  calibration  with master dark , flat and dark flat 
avoid BIAS  
Flat around   24k ADU  and around 3-4 secs
  and very important the quality of the led panel 

CS, Brian
Renaat Vandewiele avatar
Renaat Vandewiele avatar
Thank you for the replies. my issue is probably the flat frames… i take them with a white tshirt, but probably ist to light …
will look further into it