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Old 12-06-2024, 08:10 PM
bertinspace (Arnold)
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Help with Flats & Darks (294MC)

Just setting up my new (used) 294MC camera...

I noticed my flats (that auto exposed at 300ms) at gain 121 have a large round white glow in the centre of the stretched preview. This same glow appears in shots of deep sky as well.

The 120second darks also have a strage artifact in the centre of the image.....

is the sensor damaged?
Attached Thumbnails
Click for full-size image (thumbnail_Flat_300.0ms_Bin1_294MC_gain121_20240612-194954_-7.8C_0010.jpg)
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Click for full-size image (thumbnail_Dark_120.0s_Bin1_294MC_gain121_20240612-193035_-10.0C_0003.jpg)
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Click for full-size image (thumbnail_Light_NGC3576_120.0s_Bin1_294MC_gain121_20240612-201218_-10.0C_0004.jpg)
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Last edited by bertinspace; 12-06-2024 at 08:22 PM.
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  #2  
Old 13-06-2024, 08:14 AM
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AstroViking (Steve)
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Hi Arnold,

You'll need to use longer exposures for your flats. The '294 and '183 series of cameras from ZWO/ASI are well known for not giving good images if the exposure time is under 3 seconds.

For my '183MC-Pro, I use 5 second exposures for the flats and dark-flats.

I can't help with the UFO-like glow in the centre of the frame - that's odd and nothing I've seen before.

Cheers,
V.
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Old 13-06-2024, 01:47 PM
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Nikolas (Nik)
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That is a frosted sensor it is either the desiccant that needs to be changed/recharged or you need to cool slower in stages.
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Old 13-06-2024, 08:30 PM
bertinspace (Arnold)
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After some experimenting.....the vignetting is normal and just exagerated by the auto stretch in ASIair. After stacking and adding to final stack the flats worked perfectly

Results attached https://www.dropbox.com/scl/fi/rirmg...=kjhlh73m&dl=0
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  #5  
Old 14-06-2024, 04:47 PM
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ChrisV (Chris)
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Look at the flats linear not stretched - the later exaggerates things. And it should already be visible unlike lights
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