I have to same OTA. I used it with the following imaging train as the Quark has a built-in 4.2x:
A) 90 mm diameter D-ERF from Baader
B) TS 80/480 triplet
1) Baader variable length T2-T2 extension
2) T2-2" adapter
3) Chromo Quark
4) Quark to 2"
5) Daystar 0.5x flattener (basically any decent one will do)
6) 20 mm extension tube
7) ASI178mm camera
The "thing" in business end of the OTA in the above image is just a DIY protective sleeve around the DIY D-ERF housing. I didn't have an image showing the D-ERF directly. And the cable is for a DIY focus motor.
So no diagonal. I would not use any diagonal unless you have to have for some reason (quickly changing to visual is the only reason I can think of). With that OTA you can build your setup like mine if you like, no need for diagonal. I choose to use full aperture D-ERF in front of the OTA - it'll give you best results most likely (lowest amount of excess heat into the OTA). If you use D-ERF in front of the OTA, you will not need any UV/IR blocking filter.
ASI178mm has a sensor with about 9 mm diagonal. Your ASI071MC pro has a sensor with a diagonal of about 28 mm. ASI120 has sensor diagonal of about 6 mm. Chromo Quark blocking filter is 12 mm and free etalon aperture is 20 mm according to the manual, see e.g. http://www.sunfield....QuarkManual.pdf so big sensors cannot be used without ROI / cropping.
With my setup I used to bin 2x2 or 3x3 my ASI178mm due to seeing conditions for best results. Thus, you need to test, but I would start with 120MC.
Remember to take flats (flat video). You will need them. It's easy via unfocusing the image a bit if the whole sun is not visible at once.
If you end up with Newton rings, you may need to tilt your camera in respect to the optical axis. If there is only a small amount of Newton rings visible, flats with take care of that (this was the case for me).
For solar push your FPS as high as you get. It's not called lucky imaging for nothing
My setup was able to produce images like this when everything was optimized and weather allowing:
All in all, it's a nice scope for solar work with Chromo Quark. I'll bet that you'll get nice images with 120MC, later if you like to continue you could consider a black and white relatively small sensor camera to optimize your setup.
Edited by cmas, 27 January 2021 - 07:31 AM.