C-11 or C-9.25 on an Atlas(EQ-6) mount???
Posted 02 March 2004 - 08:40 PM
Posted 02 March 2004 - 08:54 PM
Scott, I would love to have the 11" SCT!
Posted 02 March 2004 - 09:19 PM
I actually want the 11", but I could "suffer" with the 9.25".
I have seen pictures of both OTA's on the EQ-6 and they look really good. I mean REALLY GOOD!!!!!
Posted 02 March 2004 - 09:33 PM
Posted 02 March 2004 - 09:47 PM
Has anyone mounted a Celestron C-9.25 or C-11 OTA on an Orion Atlas(EQ-6) mount? How do you like the combo? I may eventually go this route for DSO's.
I had a Meade 10" SCT on one - plus a 4" APO on top of that because I didn't have a side-by-side plate lying around. The only problem I had was I ran out of room on the counterweight shaft!
Meade's SCT's are heavier than Celestron's - I'd say the 10" is very similar in weight to the C11 I had (carbon fiber). The mount was perfectly happy with the load.
Posted 02 March 2004 - 10:50 PM
What is your opinion of the whole situation?
Trying to decide on a possible future purchase:
10" Orion newt
One of these would be mounted on the Atlas where the CR150 now sits. Then again, I may keep the refractor as it is a great performing scope.
I think I am going through "I don't need a new scope, but it sounds like fun" syndrome.
The CR150 gives fantastic views and does well on the DSO's that I like.
Posted 02 March 2004 - 11:04 PM
I have a bias toward SCT's and notice you don't have one yet...
I lean toward the C11 myself; I've owned a few of those and they were all very nice performers. The C9.25 is interesting but I think any advantage it might have would be more geared toward film or large-chip imaging - and my experience has convinced me that large-chip imaging makes more sense on a refractor or other faster system. You might trip over an older, used Meade 10" OTA; if it isn't MCSOG coated (MCOG was standard on older ones, EMC on later units) it's probably in great shape and many were made. They don't command the prices that the C11's do but are roughly in the same performance class.
Here's a thought: how about a Schmidt-Newtonian OTA?
You'd probably want to keep the CR150; one big advantage of the EQ-6 is the ability to easily swap OTA's. I'm beginning to consider moving back in that direction myself; I kinda miss the CGE1100. The big Meade has a large "cool" factor but it isn't nearly as flexible.
Posted 02 March 2004 - 11:19 PM
I have thought about the Meade SN10 OTA, but due to the fact that it overloads the lxd-55 mount - no one has anything much to say about the optics. Everyone concentrates on improving the mount, but I have yet to see a detailed report on just optical performance of these scopes.
It looks like a decent OTA, but until I learn more from some actual owners, I will wait this out.
Posted 03 March 2004 - 12:09 AM
Posted 03 March 2004 - 12:40 AM
I see these OTAs on AM every once in awhile...What is so great about a SN? I really don't know amything about them other than they have a corrector plate on the tube openning.
They are a pretty good alternative to a fast Newt. As Newtonians get faster, it becomes more and more difficult (read expensive) to make an accurate parabolic mirror. Coma also increases with diminishing focal ratio. The SNT addresses these issues by using a spherical mirror (much easier to make accurately) and a corrector lens which corrects the spherical aberration and also reduces coma to less than a similar Newt would exhibit. A more subtle difference is the lack of a spider and the resulting diffraction.
The tradeoff (there's always one!) is the corrector. It adds cost & complexity to the instrument, and is subject to the possibility of dew.
I had a 10" SNT and probably should have kept it longer; never really used it much because I didn't have a heavy enough mount for it at the time. Brief experiments with imaging were encouraging. There's a recent review (unfortunately in the pay section) on CN which takes a pretty good look at a 6".
If I switch back to a GEM I'll probably pick one up, as it should be a good candidate for a fast imaging platform at a much lower cost than a suitable refractor.
Posted 03 March 2004 - 12:45 AM
Posted 03 March 2004 - 01:16 AM
Is there no spider vane, then? Assuming the secondary is attached to the corrector plate. Is the secondary smaller than a regular newt?
Yes, the secondary is mounted much like that in an SCT. The secondaries are fairly large; in the 30% range by diameter. This is probably because they are optimized for imaging and need to minimize vignetting. They are equipped with a low-profile focuser positioned for prime focus imaging and include an extension tube for visual use.