Random data shifting problem

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distantnova avatar
Occasionally, seemingly randomly, maybe around 1 in 10-15 pictures i randomly "shifted", the data is just not in order. Has anyone else encountered this problem (and even knows how to fix it)?

Thomas W avatar
What camera? I've seen this exact pattern once and it's not showed up again (didn't change anything). Hopefully something like a firmware, driver upgrade, or tweak of the USB transfer settings sorts it.
distantnova avatar
It's the QHYCCD600M-PH, I'm using the latest driver, changing the USB limit setting (whatever *that* does) does not change anything.

It possibly happens more often with short exposures, like only a few seconds long ones.
distantnova avatar
This is unfortunately still happening
Ethan Chappel avatar
This is caused by packet loss as the camera transmits the image over USB. It is usually fixed by a shorter and/or better USB 3 cable or switch to USB 2.
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Ioan Popa avatar
it's the cablesmile it's a bad download
Chris White- Overcast Observatory avatar
Usb2 cable will fix this.
John Hayes avatar
You didn't say how long your cable is but I completely agree with everyone else here.  As Chris said, a USB2 cable will solve the problem but it will also slow down the transfer.  The other option is to get an active USB3 cable.  That's what I use and I don't have any problems.  Finally, you can try turning down the USB transfer speed in the driver to see if that fixes the problem.  It usually doesn't do much but it's worth a shot.

John
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distantnova avatar
Thank you for your advice. The cable is unfortunately already as short as it can be, with it running through the mount directly to the PC at the bottom of it - though through an active USB hub. I may need a better *hub* and/or cable. If you have any manufacturer recommendations - or advice on how to choose/recognize a better hub or cable let me know smile
Nadir Astro avatar
Try to avoid USB hubs, use direct USB 3 connection if possible.
Also check USB and other devices settings in Windows Device Manager and uncheck USB Power Management.

Another thing that came to my mind: you didn't specify which driver you are using: native or ASCOM. USB limit, etc. settings.
Miran Brezočnik avatar
I encountered a similar problem, which I was able to fix by replacing the USB hub and shortening the cable. I haven't experienced any further issues since then. In addition, reduce the USB speed settings in the astronomical software you are using to capture images.
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distantnova avatar
Update: this was indeed fixed by replacing the old USB cable with a new one between the camera and computer!
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Dan Brown avatar
I have this issue with two qhy600 cameras. I use very short custom usb3 cables that connect directly to the computer. I will try a different usb transfer setting first and if that doesn't work I will try usb2 cables.
Does anyone know if  this issue exists with other cameras/brands? I would have purchased a Moravian camera but I wanted the ability to use the octopi. 
Thanks,
Dan