Update 07/2021:
color version made with an ASI 178 MC.
No need to introduce the target, I won't get points for originality with that one ;)
I was inspired by
Andreas Dietz's work to test the limits of my Samyang 135 mm (and of my processing...). The 6.5 microns pixels of my EOS 6D grossly underresolve the PSF of the Samyang in the center of the field. For a week-end I could borrow an ASI 178 MM. It has 2.4 microns pixels, and I was amazed to see that it is barely enough for that lens, used at F/2.8 for the occasion (see Rev. O).
I'm quite happy with the result but there is room for improvement, starting with the raw data. Bright halos around stars (see step 1. in the animation of Rev. L) are likely due to IR passing the protection window of the ASI 178 MM. An IR-cut filter would probably reduce them, thus requiring a less agressive deconvolution. Also, as I did not have much time with the camera (and still wanted to sleep some), I did not take any calibration frame (either bias, dark or flat).
The unguided acquisitions were made over three nights with my AZ-EQ6 driven by EQMOD with PEC correction enabled and dithering at every frame.
The original image is drizzled x4, with 50% droplet size (pixfrac = 0.5 in drizzle parlance), followed by wavelets-regularized Richardson-Lucy deconvolution.
Rev. L is a GIF animation showing the successive improvements from shift-and-add stacking, drizzle x4 stacking, and drizzle x4 +deconvolution.
Rev. N (28 Jan. 2020) is an experiment with additional unsharp masking.
Feedback wanted!
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