Quote:
Originally Posted by RickS
Hi Suavi,
I don't think it's worth trying for small image scales with a refractor. Unless you have a fairly exotic (i.e. expensive) design you won't be getting diffraction limited performance over more than a small area at the centre of the field. Even then, coupled with a small pixel size camera the combination will be slow. Might as well bite the bullet and go for a larger Newt or CDK if that's what you want.
Cheers,
Rick.
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Thank you for your reply Rick. It is certainly a fascinating topic and I am happily learning more about different telescope designs. I need to read more on how to properly interpret spot diagrams. Here is an interesting read on OPD (Optical Path Difference) diagrams:
http://www.cfftelescopes.eu/OPD.html
Quote:
Originally Posted by Camelopardalis
Interesting discussion. I'm assuming there must be some wavelength factor in the FWHM...although I'd expect tighter stars from shorter wavelengths...
The other night from our little back yard in Brissie I was taking some Ha and OIII subs of the Tarantula. Seeing must have been decent, as happens occasionally. Plugging them into above formula suggests I should be seeing 2.7 arc second stars. PixInsight's subframe selector measured my best of the night at 1.9 and the mean of 2.3 over ~100 subs.  |
Great result Dunk
Recently I was getting around 1.7 Half Flux Radius for the NGC1763 in Ha which I think is not too bad neither.