ASI290MM Mini guiding frame rate drops to zero

chrisp

Hi
I have used an ASI290MM Mini as a guidecam in an OAG for eight months, most recently in combination with an ASIair Plus.
It has worked pretty much flawlessly until the last two nights.
Using multistar guiding and a 2-4s exposure it usually returns guiding around 0.6 arc sec.
On the last two occasions it has run normally for a couple of hours but then the frame rate drops dramatically to zero and the guiding fails. There may be an occasional sporadic frame thereafter.
If I turn the ASI290MM Mini or the ASIair Plus off and back on normal frame rate and guiding resume for a period but then it fails again.
Both nights were fairly cold and the camera may have dropped below the lower limit of -5C. Could this cause this sporadic problem? If so would applying a dew heater strap to the guidecam on cold nights help?
I changed the usb lead to the camera but this made no difference.
Thanks for any help

w7ay

chrisp If so would applying a dew heater strap to the guidecam on cold nights help?

It would help if dewing of the objective lens is the cause of the problem.

Since the guiding starts working again right after you reboot the ASIAIR, I suspect it is some other problem that is not caused by dewing.

(1) buy a USB-C to USB 2.0 Type-A cable from Amazon or Mouser or Digi-Key that is just long enough to reach between the guide camera and the ASIAIR. (2) plug the USB-2.0 Type-A side of the cable directly to a USB 2 port of the ASIAIR (the ones with the black plastic insert instead of the baby blue plastic insert (those are USB 3 ports). Do not use any cable that ZWO includes in the ASI290 box, and do not use the main camera's USB hub.

See if that helps.

ZWO uses commercial components in their cameras (spec'ed only down to 0ºC), and you are pretty much depending on hopium, and internal heating that they work below 0ºC. On top of that, the USB ports in the ASIAIR are marginal (my guide camera, a ASI178MM, drops off the bus even at room temperature with the newer generation ASIAIR that uses ZWO's own USB daughter cards when the USB 3 cable is over 1 meter in length -- I had no problem with the second generation ASIAIR (which used the Raspberry Pi 4 board) for a couple of years, the failure occurred when I switched to the third generation that used the Raspberry Pi CMM processor, and newer "ASIAIR Plus" that does not even use the Raspberry Pi processor.

A USB 2 cable solved my problem (the ASIAIR guiding rate is limited by the wimpy processor, and not by the USB cable anyway).

Chen

chrisp

Thanks very much for the rapid response Chen. I will get a shorter better USB cable as you suggest

Chris