Quote:
Originally Posted by Renato1
How far, magnification-wise, have you pushed your 80mm refractor
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I’d say you are using less-than perfect optics.
Firstly, real magnification tests are usually done using double stars and for these, to stand any chance at the Dawes criterion the scope must be at about X3 per mm of aperture, or a tad more, in order to distinguish the difference between the Airy disk of a single star vs a double. Note in this the disks are overlapping- not separated.
This is a really tough test and to be honest I’ve seen very few modern scopes that can usefully reach Dawes limit; most cannot. It also means some of the antique old refractors from 150 years ago really did have superlative objectives - while they were doublets, at f/15 or more some really were extremely good with a superb polish on the surfaces to avoid scattered light, which plagues open-tube reflectors.
For your 80mm that suggests 240-260X so at 200X you are getting close to the useful upper limit.
But as for your achro... well you can join the dots.
I have a 70mm quad APO which I’ve used at 200X on Jupiter, Saturn and Uranus. It does these surprisingly well for such a small aperture.
Extreme magnification is also the reason why I have my current scope.