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Old 03-05-2021, 10:53 AM
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Slawomir (Suavi)
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Slawomir is offline
Join Date: Sep 2014
Location: North Queensland
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Originally Posted by Emuhead View Post

3 scopes:
8" f4, 8" f5, 8" f6.
Given aperture determines resolution.. do they all provide the same level of detail ultimately? That is assuming the sensors pixel scale stays between 1 & 2 arc sec/pixel via binning & drizzling where needed, and just imaging longer on the slow scope vs the fast scope to ensure the overall SNR remains consistent across all 3. If I did all that, once in post if i cropped all 3 images to the same FOV would they all basically look identical or would there be more fine details on the f6 vs f4 image?
A bit late to the discussion. Everything said so far matches either my understanding or experience.

However, I think there could be some difference in data quality between 8" f/4 and say 8" f/6. I'm not talking about quite obvious differences in SNR, but spot size. This is to do with the size of the secondary and also possibly some difference in field curvatures and the degree of coma across the frame (coma corrector reduces coma but I do not think it does eliminate it entirely, particularly further away from the optical axis). Yet these potential optical advantages could be offset by a more mechanically demanding accurate guiding of a longer tube, so in the real world it could be actually detrimental to data quality to use a slower Newtonian.

I feel that it is common to chase higher SNR with ever faster f-ratios, but having settled on the aperture size, perhaps we could be sacrificing a bit of detail with the faster optics. Or perhaps there is a potential for greater gains in resolution in images from a more precise guiding, be it a better mount or adaptive optics
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