I've been dealing with some issues regarding my imaging setup. I could use your opinions on this. The issue is regarding imaging only as I don't do visual at this time.
Issue:
- Uneven / ununiform image with Quark (well nothing new here). This can be partly mitigated via flats etc. so not totally frustrated with this.
- Severe uniformity issues with the Quark & focal reducer. I am frustrated with this.
- Severe lower tight hand corner issue. I am frustrated with this.
- I have tested the setup with Sharpstar 61 mm EDPH II (FPL-53 triplet, f/5.5, 335 mm focal length) which is my "full disk Quark setup" with and without the reducer.
- I have tested the setup with Starwave 102 mm (FPL-51 doublet, f/7, 715 mm focal length) which is my "new" setup for "more closer views" with and without the reducer.
Case #1:
https://www.youtube.com/watch?v=OtPFU0LmPqk
OTA: Sharpstar 61 EDP II FPL-53 triplet, 335 mm focal length (f/5.5)
ERF: Baader D-ERF (90 mm diameter, 80 mm usable filter aperture)
H-alpha filter: Quark Chromosphere
Focal reducer after Quark: none
Camera: ASI174mm @ 16 bit, full resolution i.e. 1936 x 1216 pixels
Note: OTA masked to 33 mm resulting in f/10.
Case #2:
https://www.youtube.com/watch?v=QXB_Zhttgb4
OTA: Sharpstar 61 EDP II FPL-53 triplet, 335 mm focal length (f/5.5)
ERF: Baader D-ERF (90 mm diameter, 80 mm usable filter aperture)
H-alpha filter: Quark Chromosphere
Focal reducer after Quark: Daystar 0.5x reducer @ 0.5x
Camera: ASI174mm @ 16 bit, full resolution i.e. 1936 x 1216 pixels
Note: OTA masked to 33 mm resulting in f/10.
Remarks:
Visible issues with this setup. Uneven illumination / off-band issues seen in frames when moving sun across the view.
Case #3:
https://www.youtube.com/watch?v=QBQHBpb7Qi4
OTA: Starwave 102 mm f/7 FPL-51 doublet, 715 mm focal length (f/7)
ERF: Baader D-ERF (90 mm diameter, 80 mm usable filter aperture)
H-alpha filter: Quark Chromosphere
Focal reducer after Quark: No reducer
Camera: ASI174mm @ 16 bit, full resolution i.e. 1936 x 1216 pixels
Note: OTA masked to 70 mm resulting in f/10.
Remarks:
Visible issues with this setup. Uneven illumination (dark bands that do not move while the sun moves across the camera sensor) seen in frames when moving sun across the view.
Please omit any Newton rings and dust in the frames.
Case #4:
https://www.youtube.com/watch?v=r98aBIbULr4
OTA: Starwave 102 mm f/7 FPL-51 doublet, 715 mm focal length (f/7)
ERF: Baader D-ERF (90 mm diameter, 80 mm usable filter aperture)
H-alpha filter: Quark Chromosphere
Focal reducer after Quark: Daystar 0.5x reducer @ 0.5x
Camera: ASI174mm @ 16 bit, full resolution i.e. 1936 x 1216 pixels
Note: OTA not masked below 80 mm of aperture thus resulting in f/8.9.
Remarks:
Visible issues with this setup. Uneven illumination (dark bands that do not move while the sun moves across the camera sensor) seen in frames when moving sun across the view. Severe vignetting. Caused by the reducer?
Please omit any Newton rings and dust in the frames.
I do know the basics: QC with Quarks is understandably low and thus uniformity of the field is not a priority for the manufacturing due to the price point. I also understand that I'd be better using the 0.5x reducer after the quark to get the optical train running closer to f/22 for the asi174mm. In the case of the bigger OTA (80 mm viable aperture with the D-ERF is max as I have a 90 mm Baader D-ERF) I get 715/80 = f/8.9375 and with 4.3x at the Quark I get to f/38. And I'd better use some reducer and not running the whole system at f/38 to asi174mm. There is always an option to bin 2x2, but at the cost of lower resolution etc.
I am just looking what are my alternatives. One could think e.g. getting a new camera (e.g. PlayerOne Apollo max with 9 um pixels which samples critically at f/33.7) but I do not know what will be found from the Quark when changing to larger sensor compared to 174mm - most likely more uniformity issues. Thus, throwing more money to solve the issue by removing the reducer and using bigger pixels may lead to more issues with the bigger sensor (just look at the right hand lower corner and extrapolate there). So what to do, what to do...
Questions:
- The uneven frame: without reducer and omitting Newton rings (I did not use any tilt in these tests) and dust on the sensor / barlow etc does that uniformity of the field look "OK" compared to a typical Quark? I mean its not pretty but does it look like it's broken? I've used to this so as to understand the bigger picture I am asking it anyways.
- The uneven frame with reducer at 0.5x: How do these look to you? For me they are simply utterly unusable. I can image full disk with Sharpstar by positioning the disk carefully into the sensor while using the reducer but there is no change of getting anything reasonable with a reducer as part of the imaging train of the bigger OTA. The view is heavily distorted and looks to be off-band or something similar but is this just vignetting due to (I believe) 12 mm blocking filter and largish sensor while using a reducer?
- Is there something inherently wrong with the reducer which I have? I do not own any other reducers to test, though, otherwise I would have already tested this too.
Recommendations on how to proceed?