refractor ED 100 F/9

Hello,

Anyone have opportunity of compared the Ed 100 F/9 refractor with others refractor of 4" APO?

Thanks,
Paul

I've compared it to the stellarvue f/7 102ed, not exactly an apo--so I don't know if you're interested in that comparison or if you're looking at how the 100ed stacks up against more expensive offerings. But I can give you my general impressions.

Physically, the 100ed is 35" long vs the 102ed at 27.5"; the distance from a typical balancing point to the eyepiece is 16" on the 100ed vs 12.5" on the 102ed, which doesn't sound like much but comes into play when the scope is pointed near zenith. Both scopes have an operating weight about 10.5 pounds (4.8 kg)--that's including rings/clamshell, finder, and 2" diagonal, but no eyepiece.

Optically, the color correction on the 100ed, at f/9, is superior to the 102ed--there is virtually no violet visible on the moon or planets at high powers (200-250X)--and I am picky about that. Whereas the 102ed shows small amounts on those targets at those powers. The color on the 102ed is seeing-dependent, with much more visible in poor seeing. However, spherical correction is another story. I have had two lenses in the 102ed--the first had mild undercorrection, and the current one has excellent correction, yielding extremely nice detail on low-contrast targets like Jupiter. My 100ed has noticeable undercorrection; yet it yields very nice stellar images and good planetary detail. But it also throws up a little more haze about jupiter than I think it should--whether due to under-correction or smoothness (or the lack thereof) or poor baffling I don't know--but my overall sense on the 100ed is that you are taking potluck on the spherical correction--you won't get a dog, but you might not get tip-top optics either.

Mechanically, the focuser on the C100ed is just barely serviceable, a little rough and coarse--the crayford on the orion model might do better. The 2-speed standard focuser on the SV is quite nice, a little rough on the coarse focus, but very smooth on the fine focus, and it can take a lot of weight. The one-touch adjustment on the SV clamshell is really nice when you go from a 1/2 pound type 6 to a 1.5 pound type 4 nagler. The supplied clamshell with the Celestron is crap; I use rings with it, but these make it harder to adjust the balance in the field.

hope that helps
-geo