Quote:
Originally Posted by MichaelWB
Hi All.
I have a Celestron C6 which I bought 9 months ago to get back into astronomy after many years away, and I have been quite happy with it. Recently my neighbour bought a 10” GSO dob, so I took my C6 over to his place to compare scopes and eyepieces on Jupiter and Saturn that are nicely placed from his front verandah.
As both have a 1500mm f.l. It seemed like a good way to compare his standard plossls with the Meade SWA’s I got with my scope. He had seen Omega Centauri through his GSO with my 16mm Meade when he first picked it up and was very impressed, but we had never compared eyepieces to see if he might want to upgrade his.
Anyway, the upshot of this isn’t about the eyepieces in the end. It was the fact that his scope gave noticeably crisper images than mine no matter which eyepiece we used. Now, I’m wondering if this is because of the difference in diameter, after all, his mirror has nearly 3 times the light gathering of mine, or might there be something more to it. Both scopes seem to be collimated well.
As I said, I am still happy with the scope, it’s the perfect grab and go, but this discovery has taken the shine off it a bit.
Does anyone have any ideas or suggestions, or is it just the nature of the beast?
Thanks, Michael
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One difference is the respective resolutions of the instruments.
The Dawes Limit for resolution on double stars is 114mm/Diameter in mm
That puts the closest double star resolution (which also relates to small details on Moon and planets) as 0.75" on the C6 and 0.45" on the 10"
Ultimately, if both scopes are collimated (you have checked yours, right?) and cooled, the 10" will always win in a 'revealing small details' contest.
No matter how world class a 6" refractor is, a good 16" will always blow away the 6" in planetary details.
I've often said that if you are really into lunar and planetary observing, you don't buy a refractor--you buy a large reflector.
Here is a site with images of the Moon taken through, mostly, an 18" scope:
http://higginsandsons.com/astro/
Resolution like that is simply not possible with refractors of amateur size.