ZWO camera issue

[leon421]

Hi - I'm having an issue with dropped frames with a zwo 120mini in PHD2. The video mode always works fine, for example in SharpCap.

https://openphdguiding.org/logs/dl/PHD2_logs_RHWH.zip
https://openphdguiding.org/logs/dl/PHD2_logs_Gohd.zip 

Some frames are grainy, some are 'half-readout' images where there's a line going through the image, and a number are dropped (no frame downloaded, frame is dark red in PHD2)

I've tried two different cables and switched the USB port. I also have a ZWO ASI 120MM-S. This camera works fine with the exact same cable and the same usb port. (However I need a barrel-shaped camera to get the off-axis guider to focus)

Another thread I found makes me think it is a USB bandpass limitation. The description is similar and excerpt matches my situation, except for the images being "half" read-out. Or the camera could just be defective. When taking 6 second exposures, quite a few drop shortly after starting the exposure. "Using sub-frames is one alternative but that will prevent you from using multi-star guiding."  reduces how often bad frames happen.

The issue occurs with the ZWO and ASCOM drivers.

[bw_m...@earthlink.net]

Thanks for moving this to a new thread.  Unfortunately, you’ve got quite a mess here so you will have to do some trouble-shooting without having an imaging app involved.  To start, you should be sure your ZWO drivers are completely up-to-date and you should update PHD2 to the 2.6.11dev4 release.  That is needed in order to keep PHD2 in-synch with the rapidly changing world of ZWO camera drivers.  Once that’s done, you should be binning the camera – the new-profile-wizard warned you about that.  So re-run the new-profile-wizard and fix that.  Once that’s done, start using 2-second exposures.  Next, it looks like you haven’t done a PHD2 calibration since January.  I suspect you’re a beginner in all this so you should start each night’s session with a fresh calibration.  Then, disable the ‘Star Mass Detection’ feature on the ‘Guiding’ tab of PHD2 Advanced Settings.  If you look carefully, nearly all of the displayed lost-star events show “mass changed”.  The star mass detection feature has been deprecated and isn’t going to help you.  That said, it may be reacting to these half-frame data transfer problems.  Using an app like SharpCap doesn’t tell you anything because it operates the camera in streaming mode.  PHD2 does not do that, it operates in single-exposure mode.  Single-exposure mode requires more back-and-forth control traffic with the camera which means the USB link has to be working correctly in terms of timing.  I notice you aren’t using either a dark library or a bad-pix map in PHD2 – that’s a poor choice.  If you want to switch between cameras for testing, build separate PHD2 profiles for each camera setup.

 

https://openphdguiding.org/development-snapshots/

 

If you are using two ZWO cameras at the same time, you have to be really sure that PHD2 is connected to the right one.  The ZWO drivers are prone to switching things on you if problems arise.  So if PHD2 is suddenly connected to the imaging camera, you will obviously have problems.  That’s another reason it’s important to update all the camera-related drivers and move to the PHD2 dev4 release.  If you stopped using a dark library because you were getting warnings about having to rebuild it, that’s a strong clue that the ZWO software switched cameras on you.

 

Underlying all the operational problems, I think you may have a USB problem of some kind on your system.  You should start running daytime tests using only PHD2 connected to the guide camera – just start looping 2-sec exposures and let it run.  If it works correctly, you will at least know the camera is ok.   There is a long section in the PHD2 User Guide that talks about how this testing can be done.  Notice that it includes power delivery to the camera which is as important as the underlying USB bandpass.

 

https://openphdguiding.org/man-dev/Trouble_shooting.htm#Problems-_Camera_Timeouts

 

Good luck,

Bruce

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