Quote:
Originally Posted by Camelopardalis
Indeed, as you can see, surprisingly hard 
I recommend you read up on Airy disk (even Wikipedia has a good page on this). The mathematics of optics means that the Airy disk size is related to the f-ratio of the scope, not the aperture.
Of course, the mathematics assumes perfect optics and steady (no?) atmosphere. In practice, we don’t get either, so practice is always worse than theory.
The bottom line is, a fast f-ratio scope will give you tighter stars than a slower scope. Getting a larger, faster scope is (sort of) win-win. To a point. With the increasing focal length you are more likely to notice the turbulence of the atmosphere that degrades the view/image - this is “seeing limited”.
Btw, you’re not alone in wanting more bigger...it’s called aperture fever  |
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Let’s quote a few paragraphs from above mentioned Wikipedia article:
Mathematically, the diffraction pattern is characterized by the wavelength of light illuminating the circular aperture, and the aperture's size.
An optical system with resolution performance at the instrument's theoretical limit is said to be diffraction-limited.
The diffraction-limited angular resolution of a telescopic instrument is proportional to the wavelength of the light being observed, and inversely proportional to the diameter of its objective's entrance aperture. For telescopes with circular apertures, the size of the smallest feature in an image that is diffraction limited is the size of the Airy disk.
In short - small aperture = DSO data is always diffraction limited (unless seeing is horrible) = less detail, while large aperture = data is seeing limited = more detail.