Celestron C11 on a CGE or EQ6 mount?

OneOfOne (Trevor) · #1 08-07-2007, 10:57 AM

HI guys,

After having a bucket of fun with my C8N-GT I am thinking of upgrading. One of the things I have always disliked about the Newtonian is the diffraction spikes (they look great in photos, but I find them annoying visually). So I would like to try a different "type". I would like to try my hand at astro photography in a year or two.

I would "love" an APO, say 150mm, but this would be a huge expense (which the minister for finance may not agree to) and a huge OTA. The 8" just fits in the boot of the car, good thing I didn't opt for the 10! At the moment I am thinking of an SCT of some sort.

As the current scope is 8" I would, of course, like to pick up a bit of improvement in light gathering. I know the Celestron 9.25 SCT is legendary in its abilities and if I was coming from 6" the improvement in light gathering would be great, but coming from 8" the improvement is nowhere near as great. As a result, I am leaning toward the C11 at the moment. The OTA comes in at 12.5kg compared to my existing Newt that tops the scales at 10kg...so the weight increase should still be manageable.

Does anyone have a C11? How does it go for putting it onto the mount? Is it reasonably easy to transport? How many "stars" would you give it?

The other thing is the mount. The suggested mount is the Celestron CGE which is 19kg, 6 more than the CG5. A fairly heavy beastie, but should be manageable. Would this perform ok on an EQ6? What brand would you recommend for the EQ6? How does the CGE and EQ6 compare? Are they comparable? (The CGE is quite a bit more expensive)

I was going to ring for a few prices next week but I thought I would post something over the weekend to see what you guys think and suggest.

Budget? Up to $10k (I got onto a good thing on the stock market, so the scope is "free").

Of course, this will mean I will be selling my Newt, goto mount and other "Newt" related tools, so keep your eyes peeled on the for sale... I will probably keep the old scope for a few months to do some comparisons.

matt · #2 08-07-2007, 11:16 AM

With a budget of up to 10K, you could give serious thought to a Losmandy G11 with the C11.

That would be a very nice match which would allow the additional bits and pieces (guidescope, cams etc) you will want to add on later.

The G11 will also allow for a heavier OTA in future, should you wish to go in that direction.

The G11 will allow you room to move. Of course, it's a little less portable than an EQ6, G8 etc, but plenty of guys still cart their G11s around.

Just one option. Others will offer theirs in due course.

g__day (Matthew) · #3 08-07-2007, 12:17 PM

Strongly suggest you read the first post here, ranking and comparing goto mounts:

http://www.iceinspace.com.au/forum/s...ead.php?t=8135

The CGE is more modern than the G11 + Gemini alternative, but the G11 has better gears - hence better tracking and pointing ability.

The CGE will carry more load, and is more rugged and fool proof and has clean uncluttered lines, it just seems to need enough current to run well. The G11 has a great reputation, but I hear (second hand) of burning out motors if it wasn't balanced well on set-up.

The CGE's pointing ability may improve 300% with a supercharge - implying their quality control is severely lacking from the factory - hence its ordinary PE - barely surpassing an EQ6 - from the factory (+/14 RMS arc/secs vs about +/-22 arc/secs for the EQ6).

For good astrophotography with a large SCT you need a really impressive mount. Periodic Error in the worm drive can be estimated by the research done here

http://demeautis.christophe.free.fr/ep/pe.htm

If you're interested in the gears various mounts use - and that is critically important consider this data on many mounts that support PEC

http://www.siriusimaging.com/Help/PE...Equiipment.htm

I strongly suggest you research more before you buy. You want fit for purpose and you need to know more to get the maximum out of your budget.

matt · #4 08-07-2007, 01:11 PM

Quote:

Originally Posted by g__day

Strongly suggest you read the first post here, ranking and comparing goto mounts:

http://www.iceinspace.com.au/forum/s...ead.php?t=8135

The CGE is more modern than the G11 + Gemini alternative, but the G11 has better gears - hence better tracking and pointing ability.

The CGE will carry more load, and is more rugged and fool proof and has clean uncluttered lines, it just seems to need enough current to run well. The G11 has a great reputation, but I hear (second hand) of burning out motors if it wasn't balanced well on set-up.

The CGE's pointing ability may improve 300% with a supercharge - implying their quality control is severely lacking from the factory - hence its ordinary PE - barely surpassing an EQ6 - from the factory (+/14 RMS arc/secs vs about +/-22 arc/secs for the EQ6).

For good astrophotography with a large SCT you need a really impressive mount. Periodic Error in the worm drive can be estimated by the research done here

http://demeautis.christophe.free.fr/ep/pe.htm

If you're interested in the gears various mounts use - and that is critically important consider this data on many mounts that support PEC

http://www.siriusimaging.com/Help/PE...Equiipment.htm

I strongly suggest you research more before you buy. You want fit for purpose and you need to know more to get the maximum out of your budget.

I'm guessing you have a CGE?

Some food for thought there, though. I'll most likely be replacing my EQ6 quite soon.

Will be looking for a bigger and more accurate unit for imaging with a much heavier OTA than the 9.25.

g__day (Matthew) · #5 08-07-2007, 03:31 PM

No - I'm still on my original CG5. I'd love a more advanced mount. The comments on the G11's weaknesses and strengths come from several users of them here to me when I was first researching my next mount.

Personally I'm divided as to my next mount (I get the feeling an EM-200 or Vixen Atlux would be worth the extra dosh). At a minimum the Vixen Sphinx SXD might be by far the cheapest and most capable in its barely sufficient weight range. The Losmandy G11 appears to be the most affordable serious mount used by astro imagers here (followed next by the eq6 at half its price), the CGE would be great if someone in Australia could tune them well, the EQ6 appears too variable in its tracking for longer duration astrophotography unless you seriously tune it up too. I don't know of anyone here with a CGE truth to tell. A few folk have tak's or atlux's or the larger Losmandy Titans - and that just about us all isn't it? I note Mike Sidiono uses a Tak NJP - that speaks volumes to me about their quality given his seriousness about imaging.

All these observations are from a novice imager who reads alot about the subject - mostly on astronomy user groups here and the USA. Mind you its interesting that Ron Wodaski classes the G11 as a barely capable imaging platform for larger scopes (but I presume the guy is a perfectionist who resides soley on AP1200 or Paramount ME gear).

OneOfOne (Trevor) · #6 08-07-2007, 09:13 PM

Thanks for the thoughts so far, keep 'em coming. I had a look at the tables of data and they are certainly interesting.

One of the advantages of getting the CGE with the C11 as a package is that I save over $1000 compared to getting them individually. Which makes the CGE "cheaper" and brings it into budget. I might try to track down some more stuff on the CGE.

Funny, after I posted the message I have so far seen 2 members which already have C11's on and EQ6...so I assume that at least works OK for them.

g__day (Matthew) · #7 08-07-2007, 10:26 PM

Works okay - definite yes. Works well enough for planetary or bright clusters imaging - definite yes, works well enough for deep space objects (DSOs) - well that's we're you're pushing it severely.

If you need it to do moderate to high-end imaging - well the EQ6 is the entry level mount in this carrying capacity - no more or less.

With auto-guiding you can guide out consistent periodic error (PE) - even if its quite large, but the French graphs above show on the EQ6 they tested that it had both large PE and very random PE - a problem. Compare it to say the AP1200 which has 1/10 the PE and a very smooth curve, and you'll see why it costs 5 times more and has a 8 month waiting queue.

And any auto-guiding is costing you image quality, too much or a pendulum movement if you're over correcting is bad news.

casstony · #8 09-07-2007, 10:06 AM

Is there anywhere in Australia where you can have work done on mounts to smooth out a random PE? I recall that BATSC used to charge $250 to improve the Synta mounts by reworking the worms, etc.

rumples riot · #9 09-07-2007, 03:46 PM

Interesting.

I found that the PE on my EQ6 is quite small given that I am imaging at 10,000+mm.

I am about to take possession of a CGE mount and C14, and will be using it again for planetary imaging. I am sure tuning one of these up is possible on your own Casstony. Being adventurous is all that is needed. Asimov already has a CGE and he seems reasonably pleased with it.