Some frames have light band across the bottom

[PhilPaul]

I've been using SharpCap with little problem for a while. Recently, I attached a HyperStar to my C14. The EFW was disconnected and the camera was moved to the HyperStar was I use the filter tray. I would think everything looks the same to SharpCap except for the disconnected filter wheel.
All looks good in Live View and Live Stack, but when I run a sequence, the majority of frames have a sharp, light band across the bottom. It's not a light leak. The band of overexposure is very sharp and straight. The width of the band varies even with no filter change. Sometimes, a frame looks perfectly good.
In some cases, I see a pattern to the problem. When I swap filters and run another capture sequence, the pattern of good vs bad frames changes. I'm thinking the pattern might be related to exposure time. I'm using automatic exposure, gain & offset, so a different filter will usually result in different exposure times.

In one case, I found every fourth frame to be good.
Example: Good (+), Bad (-).
+ - - - + - - - + - - - + - - - (etc) for the entire sequence with that filter.
With another filter, it started as a pattern, but gradually changed:
+ - - - - - - - + - - - + - - - - - - - + - - - + - + - + - + + +

I'm running SharpCap v 4.0.9538.0 - 1/23/2023 on Windows 10 Enterprise LTSC v1809 (PrimaLuce Labs Eagle 4), ZWO ASI6200MM.
I'm attaching some examples.
One good frame and two bad frame showing the approximate minimum and maximum bands.
Also below is the text of one of the CameraSettings.txt files.

Has anyone seen this problem or have a suggestion of what the problem might be?
Thanks!


[ZWO ASI6200MM Pro]
FrameType=Light
Pan=0
Tilt=0
Output Format=FITS files (*.fits)
Binning=1
Capture Area=9576x6388
Colour Space=MONO16
Hardware Binning=On
High Speed Mode=On
Turbo USB=100(Auto)
Flip=Vert
Frame Rate Limit=Maximum
Gain=100
Exposure=164.266s
Timestamp Frames=Off
Brightness=10
Window Heater Power=On
Cooler Power=75
Temperature=-9.9
Target Temperature=-10
Cooler=On
Auto Exp Max Gain=500
Auto Exp Max Exp M S=30000
Auto Exp Target Brightness=82
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=C:\Users\PrimaLuceLab\Desktop\SharpCap Captures\darks\ZWO ASI6200MM Pro\MONO16@9576x6388\5.0s\gain_0\MasterDark_25_frames_-10.1C_2023-07-18T11_31_24.fits
NegativeDisplay=0
Display Black Point=0
Display MidTone Point=0.0100204060558117
Display White Point=0.99609375
Notes=
CPWI Focuser=32623
CPWI=RA=20:47:07,Dec=+30:21:32 (JNOW)
TimeStamp=2023-07-21T10:26:59.2656364Z
SharpCapVersion=4.0.9538.0

GOOD FRAME:

Western_Veil_Ha_00015_03_45_08_-St.jpeg (240.28 KiB) Viewed 6512 times

FRAME WITH ~MINIMUM BAND

Western_Veil_Ha_00014_03_42_20_-St.jpeg (232.98 KiB) Viewed 6512 times

FRAME WITH ~MAXIMUM BAND

Western_Veil_Ha_00013_03_39_33_-St.jpeg (224.68 KiB) Viewed 6512 times

[admin]

Hi,

I wonder if this is an issue with the data transfer between the camera and the PC? You have probably changed your USB wiring to move the camera from the back of the telescope to the front on the hyperstar - possibly adding a new extension or longer cable or hub. I can also see from your settings that you have the 'Turbo USB' setting to auto and that it is at the maximum of 100. The first thing I would try is to turn that setting off of auto and set it to the minimum - this will make frame transfers to the computer take longer, but may make them more reliable. It's not ideal if you were doing high speed video imaging, but for deep sky you will hardly notice the difference. If that doesn't help then check the actual wiring and insert a (good quality) USB3 hub if the length of any USB3 cable run is more than about 3m (3.5m sometimes works OK, 4m is very dodgy for USB3).

Hope this helps,

Robin

[PhilPaul]

Thank you, Robin.
I'll try the Turbo USB settings (hopefully soon) and reply with the results.

The cable is the same one I've used in the past and plugged into the computer near the top of the OTA, so cable reach was no problem. It's probably about 1m in length. The cable is double-shielded and has ferrite chokes at both ends. I had to replace the USB-3 cable which came with the camera because lack of shielding on the old cable caused interference with the WiFi.

[PhilPaul]

Thanks again, Robin!
The Turbo USB setting appears to have resolved the issue.

- Phil