Fri, 12/11/2020 - 07:54
I am thinking to get the new QHY294 M Pro to replace my Atik 383L. As I have no experience with the new CMOS sensors I wonder whether they are good for photometry. I am particularly concerned about the amp glow. Although it can be reduced with dark frames I have learned that it cannot be completely eliminated and I wonder if that can impact the photometry.
Hi Gianluca,
I'm also looking at the QHY294M, as a replacement for my STT-8300 with a failing board (again!). This camera is certainly an appealing option: 14-bit AD, great quantum efficiency (~90% vs. ~60% for the STT-8300), good size, and decent full-well capacity. However, I'm also a bit concerned about amp glow, as well as all of the other unknowns (for me, anyway) with CMOS detectors. The amp glow, at least, looks like it's not too big of an issue - and is supposed to be pretty consistent at the same temperature, exposure and bias setting. My understanding is that the biggest issue is that the glow may not be linear, certainly not when changing bias values, so you should make darks with the same settings as the light images (i.e.: don't use scaled dark frames).
Several of the BSM scopes are now using the QHY183M, and the data I've gotten from them via AAVSOnet has been very good. I believe a few AAVSOers are using QHY600s and getting good results. However, does that mean that every mono CMOS camera will be suitable for photometry?
Arne posted a comment here several months ago that he was evaluating several CMOS cameras, including the ZWO ASI294 that uses the same chip as the QHYCCD. Hopefully, he'll weigh in on what he's found so far.
Shawn
Other than Meade & QHY which I also use, ZWO have become a favorite and are certainly comparable in quality and price. It's only a matter of determing which sensor. I am now looking at the ASI6200MM-P with the IMX455... I currently use the ASI071MC-P, 1600MM-P, 462MC, 224MC, 120MM-S & 120MC-S. Amp glow was addressed in the 1600MM Pro along with other issues i.e. dew, etc.
I finally got a chance to watch the AAVSO "Focus on CMOS" webinar last night. Arne mentioned the ASI294 but didn't have any detailed information on it. However, he had several links to other references, including an analysis by Christian Buil: http://www.astrosurf.com/buil/asi294mm/. An interesting read, and to me, it sounds like the ASI/QHY294 should be "just as good" for photometry as the 183 that has been used on the BSM scopes for many months now. The 294 has the added advantages of a greater dynamic range and larger chip. I'm still undecided whether to spend ~$1100 getting my STT-8300 fixed or putting the money towards the 294. It seems like CMOS technology is improving rapidly, and waiting a year or two might pay off.
Shawn