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Thread: Camera Hangs

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  1. #26
    Join Date
    Nov 2015
    Christchurch, Dorset, United Kingdom


    Hi Jerry.

    Odd, I had some issues with my ZWO ASI 290MM guider and ACP/MaxIm just last weekend after I updated to the latest ZWO drivers (I had been running with ZWO drivers from 2019 and thought I ought to get up to date).

    The problem I had was that ACP/MaxIm couldn’t guide, reporting that no guide stars were found, even though you could plainly see ten or more stars in the guider image on the MaxIm desktop and to complicate things further the error message didn’t appear with every guider image, some would be acceptable and others fail, even on the same target.

    After chasing that problem for several nights I finally noticed that the gain (and hidden offset) values for the ZWO ASI camera had changed by themselves to some ridiculous numbers, gain had changed to 600 and offset to 0 making the background sky in the guider image around 30,000 ADU and full of noise while the stars were saturated, but that auto screen stretch function in MaxIm was making the desktop image look ok visually.

    Once I realised what was going on it was just a matter of opening the ZWO driver settings in MaxIm, enabling the “Advanced” tab to reveal the offset slider then closing out the settings tab, finally in the desktop pop-up for the ZWO driver that appears when the ZWO camera is connected in MaxIm I could adjust the gain and offset values back to sensible figures (gain = 200, offset = 40) and ACP/MaxIm was able to find guide stars again.

    I find that auto screen stretch function in MaxIm a nuisance at times as it masks changes to the image quality of the guider during a run, I wish there was a way to keep it pinned to a fixed display setting but in my copy of MaxIm DL 6.30 that doesn’t seem possible, every new guide image that is taken causes the screen display to be auto stretched making it impossible to monitor changing sky conditions from the guider image. I'm sure it never used to be that way in previous builds of MaxIm where you could set the screen stretch histogram display mode to manual and it would then not change those upper and lower histogram settings for the entire run, in MaxIm DL 6.30 those settings change by themselves with every new guide image irrespective of what display mode I select in the histogram display window.

    At least those histogram display settings only affect the visual image in MaxIm, they are not permanently changing the image.

    There is another setting in MaxIm that will cause any image that is captured to be saved with a changed numerical range so that the saved image opens in other applications with the black point registered as around half the normal max ADU (~32,000) and that setting is stored in the user config files and which are never removed when you uninstall and re-install MaxIm.

    If you open an image in MaxIm and then from the File menu select the “Save as” command there is a drop-down menu where you can choose the numerical range to be used to save the image, floating or integer, 16-bit or 32-bit, whatever you choose there and then “save” with the currently open image is then applied to every image that MaxIm captures afterwards.

    From memory, (I’m not at home this morning), the setting should be 16-bit integer in MaxIm’s “Save as” file drop-down menu and once you select that and save an image manually then MaxIm should apply that numerical 16-bit integer range to all subsequent image captures, at least when operating MaxIm manually, I don’t know if that also applies to ACP when it controls MaxIm through the automation interface, or whether ACP applies it’s own numerical range (floating or integer, 16-bit or 32-bit) to the saved image.

    Maybe one of those settings has changed on your system, ZWO ASI camera Offset and Gain or the “Save as” file menu has changed from “16-bit integer” to “Floating” numerical range.

    When I get back home later this morning I’ll check my observatory computer and verify what numerical range setting MaxIm is using, pretty sure it’s 16 bit integer.


    ZWO driver.jpg

    ZWO Offset.jpg

    File Format MaxIm.jpg
    Last edited by William Bristow; Jan 27, 2023 at 11:46. Reason: Added screen grabs



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