Quote:
Originally Posted by Shiraz
the problem with a relatively fast 5 inch will be CA. There are only a couple of refractor designs that seem capable of keeping the spot size within the diffraction region over much of the visible spectral region. For narrowband though, it should be a reasonable approach. Better bet might be a 6 inch fast Newtonian with a decent coma corrector.
|
Sounds like a good advise Ray. The only four things that at the moment stop me from going the fast Newtonian path are the requirement for an accurate collimation, perfect optical alignment is a must with a fast system, narrowband filters such as 3nm ones become less effective at faster f ratios and to a lesser degree possible CA introduced by the lenses in a coma corrector. I know these things can be overcome but to me it looks like a fast Newtonian can add a few extra challenges to this already challenging hobby of ours
Quote:
Originally Posted by Atmos
This just happens to be what I've got  |
Yes, I have been looking at similar options to your telescope and was wondering whether we possibly trade quality for speed in a refractor (slower refractor having tighter stars across the visible spectrum) and the need for a more frequent refocus with temperature shift with faster refractors.
Just slowly planning my next "upgrade"...