Quote:
Originally Posted by Atmos
It is a little more complicated than simple "Bigger is Better" because as has been mentioned, it is all about flux. Aperture, FR and pixel size all come into play.
The difference between the FSQ and AP.
AP captures 69% more photons but is only 21% slower (5 v 5.5).
The difference between the the FSQ and Alluna.
Alluna captures 16x the amount of photons but is only 2.56x slower (5 v 8).
Both of those examples are considering a similar pixel size. If the pixel size is changed things also change. Putting an ASI183 (2.4 micron pixels) on the Alluna for SUPER HIGH RESOLUTION imaging and putting that up against the FSQ (keeping the KAF-16803) changes things slightly.
The ASI183 has 14x smaller surface area (pixel size wise) than the KAF-16803. Forget the fact that the Alluna is imaging at 0.155"/pixel now, the FSQ is now getting 2.25x better signal than the 16" Alluna as the photons are now being spread very thinly among the tiny pixels. Realistically it's going to be closer to 2x SNR as the IMX183 sensor has a near 90% QE against the 60% KAF-16803.
It is not a great real world example but you get the idea. It is not just about the amount of flux entering the system (the raw aperture) but the way the photons are spread (f/ratio and pixel size).
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I ran similar numbers hence have no problem with the arithmetic you've presented...but the elephant in the room is: why would one sample at a bit over 1/10th of a pixel ? or even 1/100th of pixel?
Reduction to an absurd conclusion does not make a lot of sense when so many other factors will start coming into play by doing so (e.g. pixels sooo small to have well depth of 100 electrons
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Sure, a well sampled small "fast" system can give great results..but the same sampling rules can also be applied to larger (albeit optically slower) systems, that gather buckets more light with higher resolution.