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Technical / Update Re: CMOS Blotch Problem
« Last post by The Thing on Today at 10:34:59 »Hi All,
This may come in useful to someone...
I have replaced shared power supplies (12V laptop variety) with individual ones for each power need. This affects the 'industrial' USB3 hub which powers the cameras and the TEC cooling on the ASI294MC Pro. This seems to have completely solved the blotch problem. I suspect power output ripple and variation caused by items changing their power needs is a factor. I need to do some PI processing and stretching to verify this as I have been using StarTools recently due to PI display issues.
I also now think ambient temperature affects the efficacy and stability of the TEC cooling to a great degree. I might try making an insulating jacket for the camera body so that in warm weather it's not fighting the cooling by absorbing heat from the environment. In cold weather this shouldn't be needed. With an ambient temperature of 5C the TEC only drew 50% power to keep the CMOS at -20C, at 15C it was 100%. The CMOS temperature also flips up and down 0.5C every few seconds, this might be a measurement error or the effect of the solder blobs connecting the sensor to its backplane not being effective conductors.
I have also upped the ADU count for my flats, I was using 20000 which is the default in the APT Flats Aid tool, I have increased it to 32000ADU which is about 1/2 full well depth on this camera and suddenly the flats are correcting properly again!
All good stuff.
Duncan
This may come in useful to someone...
I have replaced shared power supplies (12V laptop variety) with individual ones for each power need. This affects the 'industrial' USB3 hub which powers the cameras and the TEC cooling on the ASI294MC Pro. This seems to have completely solved the blotch problem. I suspect power output ripple and variation caused by items changing their power needs is a factor. I need to do some PI processing and stretching to verify this as I have been using StarTools recently due to PI display issues.
I also now think ambient temperature affects the efficacy and stability of the TEC cooling to a great degree. I might try making an insulating jacket for the camera body so that in warm weather it's not fighting the cooling by absorbing heat from the environment. In cold weather this shouldn't be needed. With an ambient temperature of 5C the TEC only drew 50% power to keep the CMOS at -20C, at 15C it was 100%. The CMOS temperature also flips up and down 0.5C every few seconds, this might be a measurement error or the effect of the solder blobs connecting the sensor to its backplane not being effective conductors.
I have also upped the ADU count for my flats, I was using 20000 which is the default in the APT Flats Aid tool, I have increased it to 32000ADU which is about 1/2 full well depth on this camera and suddenly the flats are correcting properly again!
All good stuff.
Duncan
