Re: Will the Mach 2 support .....

Roland Christen

Thanks for your reply,

I did not adjust the gain in the 6200M. I could not find any way to do that in MaximDL. Perhaps I need to read the manual more closely.

The 160 EDF has 51% more light grasp, so the signal/noise is considerably higher. A real test of course would be to run each camera on the same scope with similar pixel size. I will do that when I test the Starlight X-Press Pro 36 on the 160 refractor. That camera has much higher efficiency than the QSI, and the 7.4 micron pixel size will be a good match for the 6200C binned 2x2 at 7.5 microns. That said, i suspect that the 6200M would be the clear winner, not only because of the lower noise and somewhat higher efficiency, but also because you can run it binned at 1x1 on those very steady nights to get the highest resolution.

Running this 6200C on my laptop presented some interesting challenges. I could not do an automated run of consecutive images because the laptop ran out of memory after the first image was downloaded. I don't know why that is, the laptop has lots of memory but for some reason had trouble with the 359 megabyte images and would crash each time. I also could not calibrate dark frame and flat frame in one step without MaximDL crashing. Even though I was very careful to get good flat frames, the results were really strange, especially when more than 2 calibrated images were combined. All of these problems went away when I used only 80% of the chip area for each image.


-----Original Message-----
From: Luca Marinelli <photo@...>
Sent: Wed, Jun 2, 2021 5:09 am
Subject: Re: [ap-gto] Will the Mach 2 support .....

Thank you for sharing your results, Roland. I was imaging with the Mach2 and my solid tube 10in f4 reflector last night (40lbs fully loaded but with a fairly significant moment arm) and the absolute encoders on the mount make it track smoother and easier than when I use the same scope on my AP1100 without encoders. The difference encoders make in ease of use of a mount is truly remarkable. Obviously imaging results are the same, provided one guides the non-encoder mount appropriately, but it certainly takes a bit more finesse and knowledge with the non-encoder mount.

With regards to the comparison between the QSI683 and the ZWO 6200MC, I wanted to offer some considerations to keep in mind:

1) In spite of the larger diameter of the 160mm optics, the etendue per pixel is 1.76x larger for the 130mm scope given the bigger effective pixel size of the binned KAF8300 sensor. This means that the solid angle of sky seen by each pixel of the KAF8300 sensorĀ  is almost twice as big as the ZWO 6200MC system and signal will accumulate accordingly, even before taking into account quantum efficiency.
2) The ZWO 6200MC has a Bayer matrix in front of the signal. You did not mention what filter you were using with the QSI683 camera but if it was a luminance filter, you are allowing up to about 4x more wavelength bandpass than any of the R, G, or B filters in front of each of the pixels of the ZWO ASI6200MC.
3) The ZWO 6200MC is a variable gain camera. You did not mention what gain setting you were using. If you were using the camera with default gain in the ASCOM driver, it is probably gain 0 (CMOS gain 0.8 e/ADU), which corresponds to the highest full well capacity and dynamic range, but the lowest sensitivity of the camera (signal accumulation measured in ADU per unit time). It should be noted that the camera circuitry changes acquisition mode at gain 100 (CMOS gain 0.28 e/ADU) with a step change in read noise from 3.5e to 1.5e per read. This is a particularly useful gain setting when large full well capacity is not the paramount concern.



Roland Christen

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