That makes it sound like it isn’t a usb issue?

Uh no, it's the same hardware configuration. Maybe I am not being clear, but how I have my setup is a Mini PC Outside running Ubuntu 20.04 with INDI-Server - Nightly build.

If I run K-Stars on the Ubuntu computer, it works 1x1 and 2x2. If I use the same hardware (INDI-Server) same USB hubs, same everything except run my Windows PC Inside, connecting to the Ubuntu Indi-server 2x2 works just fine (NOT USB issue), 1x1 does not work (Same hardware - Not USB issue).

It's the transfer from the Ubuntu MiniPC back to K-Stars windows that fails.

It seems like it may not be the QHY driver since it is apparently an issue of server-client communication, as opposed to server-camera communication.

Not sure what gave you the impression I thought it was the driver, I always stated it was the transfer between the remote PC and the Windows PC. I think I run like you do, albeit you run a Mac inside. But it's the same idea.

The QHY600 1x1 is a 60mp download. so it's a very large file.

I’m going to go ahead and get one so will see if the transfer to Mac is also a problem. Not sure how long it will take to arrive.

It's a great camera! Even at 2x2 it has great resolution.

I got my QHY600 an 1x1 bin is working fine on Stellarmate 1.5.9 on rPi4.  Haven’t tried iMac remote.

Yeah it will work fine direct connect to the K-Stars. The issue is when you have Indi server as a remote and K-Stars on a different computer.

Thanks.

Hope you enjoy the QHY600!

I decided to switch to running kstars/ekos on the rPi4 rather than remote mode with iMac client.  This was mainly driven by the fact that firecapture now runs native on Stellarmate with the new beta but it also means I don’t have to worry about the file transfer back to the client.  In order to support high frame rate for firecapture I’m going to an NVMe ssd via usb so for non planetary imaging I can save to that (it’s a 1 TB ssd) as well and copy the files over via smb. I will use ASTAP on the iMac to live stack from the smb so I can monitor progress as I run things from the iMac via vnc.  I upgraded to an 8GB rPi so between that and the improved disk size and performance it should work fine (once I sort out a power supply that lets the usb ssd run glitch free).

One question on using this driver.  I have the QHY600M (i.e. mono).  In the INDI control panel on the Image Info tab it shows under Bayer Info filter RGGB.  If I don’t disable auto debayer it debayers the FITS.  It doesn’t seem to recognize this is a mono camera.

Hi,
from my point of view the indiserver causes the problem due to the fact that QHY600 needs for it's images more memory. Out of the indidserver.log from my mount located pc I got the entry:as this limit is coded in indiserver.c which is 128Mbyte in line 81The camera itself has with bin 1x1: 9600x6422 = 61651200 pixel including overscan etc. and the pixel are 16 bit. This makes 123302400 Bytes, so very close. If you take into account that you need to encode this binary values base64, the size expands about 30%. So if the image transfer starts at a point, when the image is fully received from the driver itself, the server is always more than this buffer size behind and shuts down.
If you are accessing the data without passing the server -> you are around this possible bottleneck.

@jasem: it would be nice if you could check this theory 
Michel

That's the default value, you can pass -m to indiserver to override. In Ekos, the default is to set 1024MB when it starts a local instance of the INDI server.