I havent spent much time on this forum in the last couple of months but I have noticed a lot of 300mm GSO Dobs popping up. I don't know what every one else thinks but after using mine for a while now I reckon the optics are top notch
I've been getting spectacular detail on Jupiter with it, but I am still waiting for some good clear, dark and moonless skies to really give it a go on DSOs, esp galaxies.
The current line of Saxon 8" Dobs are f/6. Hopefully they have better optics too.
Geoff, can you elaborate on what you mean by saying that you cannot fault the star test? Do you get the same ring pattern either side of focus? I don't with either the 8" or the 12".
FWIW, Peter, (a WAACer), has a 12" n the optics are great. I've used it a few times with my Meade E/Pcs. The views are fine & crisp with equal diff circles either side of focus. Got a big suprise. Nicely collimated as well. All he has to do now, is upgrade his E/Pcs..... L.
Geoff, can you elaborate on what you mean by saying that you cannot fault the star test? Do you get the same ring pattern either side of focus? I don't with either the 8" or the 12".
Yes Steve, I get the same ring pattern allowing for the fact that the inside focus rings are always a bit fuzzier due to atmospherics.
What Im looking for is the distribution of brightness of the rings, especially the innermost and outermost ones, and it appears to be identical on both sides of focus as best as I can tell.
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Ah well my scopes seems to work well for observing thing other than defocused diffraction rings
Lol yes, we dont purchase scopes just to look at diffraction rings do we?
The Saxon dob I mentioned earlier showed obvious spherical abberation under star testing, but it did give me the best view of Jupiter I have seen to date, as its the seeing holding our scopes back 99% of the time.
Steve, Might just be a little out of collimation??? L.
I don't think it is a collimation issue, because the rings are concentric at high powers.
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Originally Posted by Starkler
Yes Steve, I get the same ring pattern allowing for the fact that the inside focus rings are always a bit fuzzier due to atmospherics.
Mine look a lot fuzzier inside focus, esp. the 12". But if this is due to seeing then it makes sense the 12" would be more affected. I guess I'll have to have a look how the "good" scopes compare.
I know this is a GS thread, but I have to concur with Starkler.
My Skywatcher 8" shows the same inside focus fuzziness on a star test compared to the outside focus, which is always very impressive.
The scope is collimated and I get very nice visual images with it, but there is definitely a difference. At least the fuzzy inside image is nice and bright and the inner and outer circle are very circular and concentric. I can still see the airy disc at the centre.
I have noticed the fuzziness varies with the seeing, and on some evenings the number of rings visible is better than others. So it must be as Starker suggests attributable to atmospheric conditions.
If I'm splitting antares (at 200x), getting nice detail on jupiter and saturn, and seeing loads of detail in DSOs... wouldn't my scope be fairly well collimated?
L.
Ken & Geoff, I'll have to have a look at a star test in your scopes one day.
