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Super Light Cup vs Light Cup

Started by ronbee, 02/05/2005 07:40AM
Posted 02/05/2005 07:40AM Opening Post
I've been using my new 5.1" TMB130LW Super Light Cup almost every night for almost a month now. Unfortunately, seeing was pretty bad most nights (except for that one good night with binoviewing Moon). Well, tonight it appeared the seeing would support 195x with my 4mm SuperMono on Saturn (most nights I could hardly get to 156x :-( this year). The view was great when the seeing steady momentarily.

Well, I decide to pull out my old pal, my dear pal, the 4" TV-102 Light Cup. Not having another diagonal (waiting to get the new TMB) nor another mount, I had to pull off the TMB and put on my Light Cup. Wow, the counterweight almost tip over and had to rebalance ;-). At 176x (5mm SuperMono) and 220x (4mm SuperMono), the 4-incher was no slouch! But immediately, without even a side-by-side, I noticed that (A) the TMB130LW despite being a fast f/6 was better color corrected than my 4" f/8.6 TV-102 doublet - amazing!!! and (B) despite the fact that the R&P focuser on my TV-102 is so smooth - there just ain't no going back once you've tasted the Feathertouch "fruits of knowledge" ;-), simply no contest. I spent about 15 minutes with my TV-102 and I could fairly easily see the "wirely"
look in the A ring, the Crepe ring around the ansae was obvious but harder when crossing the globe. There might have been shading in the B ring around the ansae but I wasn't sure. The SEB was obvious on the globe with gradually darkened shading going toward the pole. Now I never did see green polar cap with the 4-incher.

Switching back to the 5.1" TMB130LW, I noticed that the planet was a little more unstable due to seeing. Umm, seeing may really affect the aperture. But when the seeing settled just momentarily, at 195x (4mm SuperMono) I could see the Cassini Division as gap; I always see only line in the 4-incher. A ring looks even more wirely and the B shading was so obvious. The Crepe ring was brighter and much easier to see across the globe. SEB obvious. But upon closer
look, the ultra super low contrast EB could be seen just south of the Crepe Ring and not seen tonight in the 4-incher! Though 260x (3mm Radian) wasn't able tonight, I could see that Saturn was actually brighter through the TMB than the 4-incher at 220x! And the dull green polar cap color through the TMB! I so desperately
wish Thomas Back would design a 3mm SuperMono someday (even if he needs 4 elements!).

I guess a future side-by-side in excellent seeing will be called for ;-), wouldn't you say?

I had always wondered why E. E. Barnard spent almost a year of his salary to buy his first 5-inch refractor. Surely, 4-inch in those days would cost much less. Now I see why ;-).

Ron the 5-inch Tall Evangelist B[ee]