Circular-ish background with live stacking

[jsadoulet]

Hello everybody

I have some weird background when shooting at NGC 6946 and I don't understand what happens. When treated on Pixinsight, background is showing rather circular pattern centered on the field of the telescope. I can't get rid of it.
Maybe I was too early in the night and dark was installing ? I use very often auto gain function. Then why circular glow ?
I join some sample of files for investigations !

Is anyone have hints or solutions ? Thanks a lot.
Jean-Paul
https://www.dropbox.com/s/vmq9x1e3xrmc8 ... d.JPG?dl=0
https://www.dropbox.com/s/1d91us7g1pbui ... s.txt?dl=0
https://www.dropbox.com/s/iw68w0ggr2458 ... .fits?dl=0

[admin]

Hi,

Sorry to say I've never seen anything like this before. I think some experimentation might help work something out though. If you are using darks and/or flats then I'd suggest running a test without them to see if the effect goes away which would then narrow down the problem to being caused by either darks or flats depending on which one makes the difference in the pattern appearing.

Cheers, Robin

[umasscrew39]

I am also using the ZWO ASI294MC Pro and I also get this pattern as well in PI when I perform the auto-stretch. I managed to get rid of the circles when continuing the post-processing procedures and the final image will come out fine (see M27 attached) but a few points here:

1- I am new at using PI so I am still experimenting/learning and I may post this on the PI community for advice

2- By experimenting (which Robin suggested as well), I mean things like:

a) exporting the final stack in .fit format only as suggested by PI
b) exporting with and without darks and flats (I have only used darks at this point so flats are not causing the problem)
c) making sure you do not export the stretched live stack into PI (I did this the first time and things get really wacky)

Once I figure more out, I will post my findings.

Bruce

[BlackWikkett]

I've not seen this type of gradient but don't use PI. I'd try stack the same data without dark or flat calibration. There may be a weird interaction going on with the calibration frames. Also took a look at your camera settings you provided. See the bold areas. Hope you find out what causes it


[ZWO ASI294MC Pro]
Debayer Preview=On
Pan=0
Tilt=0
Output Format=PNG files (*.png)
Binning=1
Capture Area=4144x2822
Colour Space=RAW16
High Speed Mode=Off
Turbo USB=80(Auto)
Flip=None
Frame Rate Limit=Maximum
Gain=106 this is below unity and generally not recommended
Exposure=3.294998 This seems like a very short exposure
Timestamp Frames=Off
White Bal (B)=50(Auto)
White Bal (R)=50(Auto)
Brightness=4
Temperature=-11.7
Cooler Power=100
Target Temperature=-15 Really working the cooler over I'd set a warmer target temp as the cooler cant reach the goal
Cooler=On
Auto Exp Max Gain=285
Auto Exp Max Exp M S=30
Auto Exp Target Brightness=100
Mono Bin=Off
Banding Threshold=35
Banding Suppression=0
Apply Flat=None
Subtract Dark=None
#Black Point
Display Black Point=0
#MidTone Point
Display MidTone Point=0.5
#White Point
Display White Point=1
TimeStamp=2019-07-24T21:06:51.9380504Z
SharpCapVersion=3.2.5986.0
TotalExposure(s)=421.759744000001
StackedFrames=128

[umasscrew39]

I am using the same camera and my settings are considered within the normal range: Gain: 350; Temp -10 (Power 89); Exposure 60s. So, I don't think they are the problem.

[jsadoulet]

Hello everybody
thanks for your investigations and your advices !
By chance, I found that the problem disapears as soon as I load in PI the 32-bits stacks instead of the 16-bits frame fits !
Could someone tell me if there is potential drawbacks (except the file size) in using 32-bits.fits frames in Pixinsight from ZWO ASI294MC Pro ?

Thanks

Jean-Paul

[umasscrew39]

Hi Jean-Paul

Excellent! I am still under cloudy skies so I have not been able to test further. However, this makes sense given what Robin told me in the past and I hope he chimes in as I understand:

A- If you want to only tweak an image in PI: Save as 16-bit stack with adjustments such as color balance and stretching as a PNG file (option 3: Save with adjustments)


B- If you want to post-process an image in PI: Redo stretching and color balance: Save as a 32 bit raw stack (option 2: Save as Raw 32 FITS file)

You did 'B' above which I have not tried yet. I was only doing 'A' which you can still get rid of the funny circles as you continue tweaking the post-processing but I suspect it is not really the correct way to do it.

Bruce

[jsadoulet]

thank you Bruce
I hope that your sky will improve.
I will continue my tests as soon as my sky is OK. It rains hard in Lyon France.

[jsadoulet]

Hello everybody
is it possible to get rid of the vertical white strip on the right or at least to darken it as it is a nuisance at night ?
Thank you

Jean-Paul

[admin]

Hi,

Are you looking for the night vision mode? https://www.sharpcap.co.uk/news/whats-n ... arpcap-3-2

Cheers, Robin