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A nice clear night in Sydney last night so captured M17 as a test target and then full sets of Calibration frames afterwards ( Flats , Darks , Dark Flats , Bias )
Captured 2.5 hours on M17 with the 2600MC set to Lowest Read Noise or Gain 100 , cooled to -10C , with L Extreme filter
Moon was 91% overhead
Capture software APT
Flats were taken at a target 32,768 ADU as advised, and using a stretched white T shirt and a Huion dimmable light panel , dimmed down
Exposure time was 3.6 sec
Captured 40 Flats , 40 Dark Flats, 40 Darks , 50 Bias
Stacked all kinds of variations of Calibration frames ( Deep Sky Stacker )
Lights only to start with
Lights and Flats
Lights , Flats and Dark Flats
Lights , Darks , Flats
Lights Flats and Bias
Lights and Darks
To be honest none of the above produced a even flat field in fact the worst was just using Flats or using Flats and Dark Flats , absolutely terrible
Using Flats and Darks and Flats and Bias produced slightly better results but still grossly uneven on one side of the frame ( I used my processing software Startools to load each stacked file and perform a first stretch to observe the results with Calibration
Then I just loaded my Lights only stacked file into Startools and used the Wipe module set to Narrowband and it cleared up 80 to 90% of the uneven field
In other words the uncalibrated stretched image was not perfect but useable, the calibrated stretched images were horrible , some worse than others
Attached photos of a few
Lights only
Lights and Flats
Lights Flats and Dark Flats
Lights Flats and Bias
Lights only , using Wipe Narrowband preset in Startools
Any ideas ??
Maybe achieve exposure times longer or shorter
Maybe change ADU to lower say 25,000 ADU
Tonight I’m going out again to try imaging on same target M17 with Gain 0 or highest dynamic range plus maybe some different Flats
I was hoping for better results after all the help from everyone
Comments and further advice most welcome
Cheers
Martin
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