Weird banding noise artifact in live stacking?

[Andratos95]

Hello!

I have recently started using the Live Stacking tool on Sharpcap Pro, but I have a problem.
The live stack goes well, however at the end I am left with an image with some weird banding artifacts, especially visible in the noisier parts of the image. Here's an image that depicts the problem: .
The camera I used is the Player One Neptune-C II. This live stack was created with 422 subs of 5s and 250 gain.
I have NOT applied flat frames because of another problem: the resulting live view after applying the master flat resulted so incredibly dark that it was impossible to see anything (only the core of really bright stars).

I hereby attach the log file of the live stack:

Code: Select all

[Player One Camera 1 [Neptune-C II IMX464]]
FrameType=Light
Debayer Preview=On
Binning=1
Capture Area=2712x1538
Colour Space=RAW16
Output Format=TIFF files (*.tif)(Auto)
Pan=0
Tilt=0
Frame Rate Limit=Maximum
Gain=250
Exposure=5,000s
Cooler=Off
Temperature=16,2999992370605
Timestamp Frames=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
Hot Pixel Sensitivity=5
Subtract Dark=None
NegativeDisplay=0
Display Black Point=0
Display MidTone Point=0,0605536332179934
Display White Point=1
Notes=
Telescope Simulator for .NET=RA=21:15:21,Dec=+60:14:37 (JNOW)
TimeStamp=2022-09-18T22:05:19.1673223Z
SharpCapVersion=4.0.9313.0
TotalExposure(s)=2109,99999999999
StackedFrames=422
LiveStack.SaveRawFrames=None
LiveStack.AlignFrames=True
LiveStack.Derotate=True
LiveStack.StarsForAlignment=15
LiveStack.StarDetection.Sensitivity=75
LiveStack.StarDetection.SuppressHotPixels=True
LiveStack.AlignAutoDisabled=False
LiveStack.ReduceNoiseAmount=0.5
LiveStack.BrightnessLimit=78.31651
LiveStack.FilterBrightness=True
LiveStack.AutoBrightnessLimit=True
LiveStack.FWHMLimit=6
LiveStack.FilterFWHM=True
LiveStack.WarningThreshold=5
LiveStack.StackingMode=1
LiveStack.SigmaClipInitialCount=5
LiveSack.SigmaClipThreshold=3
LiveStack.SigmaClipLowLimit=1
LiveStack.AutoSaveReset=False
LiveStack.AutoSaveResetMinutes=5
LiveStack.LogarithmicHistogramHorizontalAxis=False
LiveStack.AutoSave=True
LiveStack.BlackLevel=0.5825243
LiveStack.WhiteLevel=99.75728
LiveStack.MidLevel=18.3106
LiveStack.WBB.db=0
LiveStack.WBG.db=0
LiveStack.WBR.db=0
LiveStack.Saturation=1
AutoStretch.Strength=2
LiveStack.StarDetection.FaintStarsOptimization=True

Thanks to anyone who'll help me!

[Menno555]

Hi and welcome

I'm almost sure that this is so called "walking noise". This happens when you keep on tracking or guiding the same piece of sky for a long(er) period. Here it's better explained: https://www.shutterhow.com/what-is-walk ... otography/

The first thing you could try to tackle this, is to make dark frames and apply those. Sometimes that is enough to make it (almost) disappear.
You could also try to make longer exposures. With my set-up I get walking noise with 5sec exposures. But when I use 180sec for example, it's almost gone.
But the most effective is dithering. This is a tiny random movement (few pixels) of the mount every few captures. When you use guiding, it's almost a standard to use that. You can set it up do so that the dithering happens automatically.
But if you use tracking (like I do) you can do it too but manually. For example with that 5sec exposure: I then take 5 captures, Pause the run, move my mount a tiny bit randomly, Continue the run, let it run 5 exposures, Pause, and so on.

Hope this helps a bit.
Menno

[Andratos95]

Thank you so much for your answer! I have looked into dithering, and I was wondering if it would be possible to do it with the Star Adventurer 2i, which does not support ASCOM drivers. I see that in the "guiding" tab in SharpCap settings, there's the option of "dither only (no guiding) using ascom mount pulse guiding". I have set the mount in the settings to "on camera ST4" and connected the ST4 cable from the camera to the star adventurer. Now... Can I dither in RA axis only like this? I know there's some way to do it with PHD2, but... I don't wanna bother with auto-guiding when Live stacking... Can I bypass PHD2 and dither just in SharpCap in this way? Any other step I must follow?

[Menno555]

Somebody else has to answer this because I have little to no experience with this. Somehow I have a "old soul" somehow and just love to do most things manually

Menno

[calan]

For what it's worth, even when guiding with PHD2 and using SC's auto-dither (through PHD2), I still pause the stack and PHD2, and manually bump the mount controls every now and then. For some reason, the dithering link between SC and PHD2 isn't as random as I'd like, and it can cause large offsets, even if the amount is set very low in the settings. I don't know who is in charge of the actual movement (SC or PHD2), but it isn't very predictable.

I usually look at the left-hand drift graph to see where my subs are grouping, and manually move the scope occasionally to keep it from dithering off in one direction. Also, I believe the drift graph is backwards in RA, but I haven't talked to Robin about it yet. If I am off to the left side and want to move it back toward the center, I have to actually move the mount towards the left...in the direction of the error (Regardless if I have the RA controls reversed for being on the west, etc).

Dec doesn't do this; up is up and down is down.