Newbie - bloom in stack (ASI294MC)

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degantx
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Joined: Wed May 04, 2022 1:09 am

Newbie - bloom in stack (ASI294MC)

#1

Post by degantx »

I seem to have a configuration problem with my equipment such that stacking images results in a significant "bloom" or bright area in the general center of the image. I don''t have an example at this point but found by aggressively stretching I can darken things enough to get rid of it. The problem with that is it darkens things I don't want darkened.

I have Darks captured but no flats.

With the ASI294MC I'm running 280-300 gain and bin 1. Here's the camera setting from a session where I had it. Thoughts? I'm sure it's a newbie mistake...

[ZWO ASI294MC Pro]
FrameType=Light
Debayer Preview=On
Pan=0
Tilt=0
Output Format=PNG files (*.png)(Auto)
Binning=1
Capture Area=4144x2822
Colour Space=RAW16
High Speed Mode=On
Turbo USB=80(Auto)
Flip=None
Frame Rate Limit=Maximum
Gain=261
Exposure=4.339s
Timestamp Frames=Off
White Bal (B)=50
White Bal (R)=50
Brightness=30
Cooler Power=58
Temperature=-10
Target Temperature=-10
Cooler=On
Auto Exp Max Gain=285
Auto Exp Max Exp M S=30000
Auto Exp Target Brightness=100
Mono Bin=Off
Trail Width=3
Minimum Trail Length=100
Trail Detection Sensitivity=9
Remove Satellite Trails=Off
Background Subtraction=Off
Planet/Disk Stabilization=Off
Banding Threshold=10
Banding Suppression=0
Apply Flat=None
Subtract Dark=None
NegativeDisplay=0
Display Black Point=0
Display MidTone Point=0.5
Display White Point=1
Notes=
CPWI=RA=00:14:16,Dec=+72:37:38 (JNOW)
TimeStamp=2022-05-01T03:28:35.6121053Z
SharpCapVersion=4.0.8856.0
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Menno555
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Re: Newbie - bloom in stack (ASI294MC)

#2

Post by Menno555 »

Hi and welcome

The not using flats is causing that. Flats "remove" the vignetting (that's what you see now) and also any visible dust specs.

Menno
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admin
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Re: Newbie - bloom in stack (ASI294MC)

#3

Post by admin »

Hi,

it could definitely be related to vignetting (which as Menno says would be cured by flat frames). There can be some other causes of things like this, for instance if you have a cooled camera and frost or dew is forming on the sensor or sensor window then you can get a similar effect. Probably best to share an image showing the problem with us if you can.

cheers,

Robin
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oopfan
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Re: Newbie - bloom in stack (ASI294MC)

#4

Post by oopfan »

Hi,

Tell us about your light pollution and f/ratio of your scope? Your camera settings file says that the exposure was 4.339 seconds. That indicates that you used The Brain for determining exposure. There is the possibility that the recommended exposure is too short. In that case, you are flirting with an ugly artifact called Raining Noise which would prevent you from stretching the image too far.

It would be a great help if you could upload an individual frame and the stack, if possible.

Thanks,
Brian
degantx
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Joined: Wed May 04, 2022 1:09 am

Re: Newbie - bloom in stack (ASI294MC)

#5

Post by degantx »

ya'll are too kind and give me too much credit. I shall investigate the Brain now as I've done camera analysis a few days back; had not gotten deep enough for that yet. I do have a cooled camera but I don't think it's quite frosted up but worth considering. And I wouldn't call it vignetting based on what I've seen of that.

So I shall await some clear sky Thursday and report back - if it's still funky I'll post some images.

Thank you all for the hints to pursue!
degantx
Posts: 4
Joined: Wed May 04, 2022 1:09 am

Re: Newbie - bloom in stack (ASI294MC)

#6

Post by degantx »

Found my way to "The Brain" and attached the results. I went with slightly longer exposures and higher gain to get Smartcap to be able to register stars and Live Stack. Attached are some images of Bode's Galaxy and Cigar Galaxy. I believe conditions last night weren't the best for this but the results show the problem I have. I'm 99% sure it's user ignorance so looking for a tip on where to study up rather than grinding you kind folks for answers I know I have a lot to learn.

What I'm finding is I can make this go away by sliding the left most bar further to the right - but that darkens everything. Bode's is basically missing any details - just hints (and greenish but I was tired by this point). When I overcome my centering problems you'll see that these would be right in the middle of the noise. I tried with cooler on and with cooler off to little difference.

So kind guidance to where I should study more would be great and appreciated!

Light pollution is at least Bortle 8. It's a Celestron 8SE with Reducer to f/6.3
Attachments
Stack_181frames_890s_WithDisplayStretch.jpg
Stack_181frames_890s_WithDisplayStretch.jpg (734.82 KiB) Viewed 146 times
Stack_108frames_570s_WithDisplayStretch.jpg
Stack_108frames_570s_WithDisplayStretch.jpg (938.53 KiB) Viewed 146 times
Screen Shot 2022-05-08 at 10.11.09 PM.png
Screen Shot 2022-05-08 at 10.11.09 PM.png (199.35 KiB) Viewed 146 times
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oopfan
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Re: Newbie - bloom in stack (ASI294MC)

#7

Post by oopfan »

Hi,

Yeah, you definitely need Flats. That'll cure that central hot spot. Have you taken them before? My scope is smaller. My dew shield is 100mm (4 inches) in diameter, so a 10cm x 10cm EL panel works great. For your large 8-inch scope, probably the best option at this stage is for you to take "Sky Flats". We can get you more information on that. Basically, you place a white T-shirt over the front end of your scope and point it at the sunlit sky (not at the Sun.)

Bortle 8-9 poses a real challenge for M81. You need A LOT more integration time. At Bortle 5 with a f/5.9 scope, I spent 11.3 hours on M81. Still I wish I could have spent more time. Consider brighter galaxies like M51, The Whirlpool Galaxy. It may sound boring but try your hand at star clusters like M13, the Hercules Globular Cluster.

Good luck and have fun,
Brian
degantx
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Joined: Wed May 04, 2022 1:09 am

Re: Newbie - bloom in stack (ASI294MC)

#8

Post by degantx »

Brian, Menno and Robin

The insight I was hoping to not hear for a few more sessions. So many hurdles to overcome and ever so close…

Thanks so much and I’ll take to heart the target selection and flats guidance.
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oopfan
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Re: Newbie - bloom in stack (ASI294MC)

#9

Post by oopfan »

Your welcome. AP is a constant learning experience. Each breakthrough I make, I'm happy for 24 hours, then I revert back to "it's not good enough." I think that is what keeps the Astronomy Industry in business.

Brian
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