Planetary EP's on Jupiter

Just came in to take a break from Jupiter watching, and I noticed something interesting. I've always considered my UO ortho's to be the last word in sharpness in my collection. Tonight I tried a mix of EP's just for fun: 25 mm Antares Elite on a 2.8 Klee(for 8.9 mm's); 20 mm Antares Elite on 2X Ultima (9.1 mm) 10.5 Pentax Xl; and a 9 mm UO ortho. On the scope I was using the magnification range was from 135X-114X, so there wasn't a great difference there. The best out of the pack was the 20 mm Antares on the Ultima. It was visibly better than the UO, even with the extra glass-lots of belts, festoons and whirls, and the great Red Spot as plain as day. Who'dathunkit?
Larry Seguin
Taos, New Mexico

The current UO orthos suck, it's the sad truth. I have a 70's era UO 6.5mm konig that is beyond superior to a 7mm UO ortho from the late 90s on any and all planets. Tested in a Meade 152ED that regularly splits Nu Scorpii (~>1 arcsec) and stood up well to an AP155EDT and FS152 in side by side testing.

UO doesn't make 'em like they used to, that's for sure. I'd love to find more classic UO konigs. See _Telescope Opitcs, Evaluation and Design_ for spot diagrams of orthos, plossls, konigs, naglers, erfles, and more. The ortho shows a larger on axis spot diagram than the plossl, and the konig is the smallest of all. My experiences with many UO konigs in practice seems to reinforce these findings.

Tele Vue plossls are my standard for pure 4 element greatness on planets for a reasonable price. They are as good as anything I've ever tested (not counting the zeiss or pentax orthos, or new Tmb monocentrics).

What scope is this? Some fast Dob?

The Antares Elite appear to be identical to the
Celestron Ultimas. I wonder if the Ultima Barlow
was optimized to work with the Ultima eyepieces.
Might give that combination an edge over others.

>>>On the scope I was using the magnification range was from 135X-114X, so there wasn't a great difference there. The best out of the pack was the 20 mm Antares on the Ultima. It was visibly better than the UO, even with the extra glass-lots of belts, festoons and whirls, and the great Red Spot as plain as day. Who'dathunkit?
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Some stuff to think about....

I am guessing that you are using these eyepieces in an XT-8 from your previous posts and from the 1200mm focal length. When discussing eyepieces, I think it is always necessary to include the telescope in question, many eyepieces that work nicely at F10 are done for by the time they get to F5. The mount also is important, a tracking mount that keeps the target centered means edge performance will not be so important on those planetary views.

My experience with orthos, plossls, Erfle's, Konigs and other older designs is that they are quite sharp all over in an F8 Newtonian and not so great at the edge in an F5.75 Newtonian (F5+Paracorr.) I generally use eyepieces that handle the fast light cones when using a faster scope.

In this case, the guessed at XT-8, it maybe that barlowing these longer focal length eyepieces (20mm)is helping out with the off axis performance so that with the undriven mount, you are able to get better views as the image drifts across the FOV.

Jon

Am I wrong that the Ultima barlow does not give 2X , but is closer to 2.3X ?
Seems I've heard this from several sources.

David