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I keep seeing great images from Celestron 9.25's..

Started by dwalton, 01/10/2005 02:57PM
Posted 01/10/2005 02:57PM Opening Post
Are these essentially the best mass-produced SCTs out there for planetary and lunar viewing? (Let's limit our discussion to SCTs in the 8"-12" range, since aperture might start to win out once we get to 14"). It seems like every time I see 9.25 images, they're astounding.

It would be interesting to put a 9.25 up against, say, a 10" high-end reflector in the f/6-f/7 range, and see what conclusions are reached for visual use on planets, lunar, and doubles.

Thanks,
Doug
Posted 01/10/2005 04:26PM #1
I've done it here in FL on several occassions in our club. In all honesty I would have to call it a close draw, with maybe the 10" being a little better.
Another club member has an 11" SM and it wasn't noticably better than the 9.25. They are in deed very good scopes!

Walt
Posted 01/10/2005 06:12PM #2
>>It would be interesting to put a 9.25 up against, say, a 10" high-end reflector in the f/6-f/7 range, and see what conclusions are reached for visual use on planets, lunar, and doubles>>

If you're talking visual, I would put my money on a high end reflector. Reason is Central Obstruction. Two years ago I brought two high end 10" Mak-Cass scopes down to the Florida Star Party. One was an F9 with 31% obstruction, the other an F14.6 with 23% obstruction. The scopes were set up side by side. On things like delicate detail on Jupiter, you could see the difference quite readily in the amount of subtle detail and contrast visible. When we aimed both scopes at Sirius, the companion was easily visible in the 23% F14.6 obstructed scope, and very difficult in the 31% F9 scope.

The C9.25 is even worse than 31%, something on the order of 38%, I believe. As such, it would not stand a chance against a well made high end Newt with 20% or less obstruction.

Just because there are great images coming out of this scope does not mean that you will visually see this kind of contrast and detail with your eye. In order for the eye to discern subtle detail the inherent contrast must be very high, and a largish central obstruction will definitely kill it real quick, no matter how well the optics are figured. An imager can stack thousands of images and crank up the contrast until even the minutest detail pops out. There is no such contrast enhancement feature in a human eye/brain system.

Roland Christen
Posted 01/11/2005 05:37AM #3
Doug,
If your discussion is centered around SCT's of this aperture size, I really like my C9.25". I have previously owned a Meade 8" and a Celestron 8" Ultima. The Meade I returned in 2 days due to horrible (ok, non-existent) quality control. Don't even get me started on that useless thing. The 8" Ultima is nice, but I am not a fork mount person. I moved on to 4" APOs (Vixen, Tak). Last year I purchased a C9.25" to mount on my Vixen Sphinx, for webcam planetary photography and for visual viewing (double stars and planetary nebula). I have truly enjoyed this scope and will never sell it. It is like a Honda Accord EX, not entirely in the ultra-luxury division, but a solid and reliable performer and makes you want to use it more and more. Finally, I think the OTA size is just about comfortable to mount and manage for me. A big guy with a good back might be ok with a C-11, not me.

The Tak I will get rid off once I get an AP 130 sometime in the future smile , I'll keep the 9.25".

Good luck! Ivan



Posted 01/11/2005 10:26AM #4
I like my C9.25 a whole lot, and consider it a poor man's substitute for the wonderful Takahashi TSC-225 (no longer produced). It is a very consistent performer, but visually the smaller AP155 refractor has better contrast and on most nights is better for planets in my Midwest USA seeing. But I always bring the C9.25 just in case conditions are favorable (seeing & cooldown), and of course it is brighter for DSOs.

Like Ed Ting said, the C9.25 is the SCT for folks who hate SCTs.



Posted 01/11/2005 03:16PM #5
Why is this scope so good compared to all of Meade's SCT's and Celeston's other scopes? They sure charge a premium for it.