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 Bob D
sage
Reged: 05/24/08
Loc: Dallas, Texas, USA
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Re: "smoothest guiding" mount for $2K, $3K, and $5K?
[Re: chicot]
#3163858 - 06/15/09 12:22 PM
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Have you tried your CPC on a wedge? From what I'm reading about the lower-end GEM's I'm wondering if they'd really offer that much better tracking than your existing fork mount.
I haven't yet tried the CPC on a wedge. From what I've read, you need a very good wedge, which means that an Atlas or CGEM wouldn't be a huge additional investment. However, what I'm mainly thinking about is getting an EQ mount for longer exposure deep-sky with a refractor. Initially, I would probably just start with a 600mm f/8 camera lens on the EQ mount, while deciding on a "bigger refractor." 
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chicot
sage
Reged: 09/30/08
Loc: Liverpool, UK
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Re: "smoothest guiding" mount for $2K, $3K, and $5K?
[Re: Bob D]
#3164042 - 06/15/09 02:27 PM
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Ah, I didn't know that. Yes, if you're going for multiple ota's then a GEM is the way to go.
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Bob D
sage
Reged: 05/24/08
Loc: Dallas, Texas, USA
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Re: "smoothest guiding" mount for $2K, $3K, and $5K?
[Re: Patrick]
#3164044 - 06/15/09 02:28 PM
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Vixen is well known to have very good tracking performance. I suspect it has more to do with load capacity versus cost, plus difference in the hand controllers...Starbook versus Gemini versus NexStar.
Vixen Sphinx SXD weight capacity 50 lbs.
I had seen several old threads on CN and Yahoo that seemed to conclude that the "SXD 50 lbs." included counterweights -- so I was thinking maybe about 20 lbs. for "not pushing it" AP gear. Unfortunately, the Yahoo group also has a lot of posts about mechanical issues with SXDs.
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I wanted to respond to this because I noticed that you have the C9.25. If this is the scope that you're planning on using, I think once you get it fully loaded with AP gear you will find yourself more in the 35 - 40 lb range. I have a C6 SCT and AT66ED refractor and my gear weights 24 lbs with all total. You will probably want a CGE class mount or perhaps a CGEM class mount at the very least. Regardless of the mount, you should plan on autoguiding if you're going deep at the focal length your scope operates at. I think that's going to be true no matter which mount you use.
Patrick
As you can see from my just-prior reply, I wasn't initially thinking of using the EQ mount for the CPC925 -- just reserving that scope for whatever it could do reasonably well in alt-az, like visual and solar-system AP. So, my thinking was to get a separate scope+mount better optimized for >1-min exposure. If such an EQ mount turns out to be relatively light, then it would also be good for travel to darker sites. However, if the only way to get smoother guiding turns out to be a "heavier mount" anyway (with around twice the 20-lb, capacity), then it would also become a candidate for carrying a de-forked C925 at some future date.
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jrcrilly
Refractor wienie no more
Reged: 04/30/03
Loc: NE Ohio
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Re: "smoothest guiding" mount for $2K, $3K, and $5K?
[Re: Bob D]
#3164100 - 06/15/09 02:52 PM
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I had seen several old threads on CN and Yahoo that seemed to conclude that the "SXD 50 lbs." included counterweights -- so I was thinking maybe about 20 lbs. for "not pushing it" AP gear.
The confusion you mention is unfortunate. The "not pushing it" load for the SXD must be greater than 20 pounds, though. The straight SXW is conservatively rated at 22 pounds for imaging (no derating required). The SXD is probably good for 30 pounds (which would make sense, as the usual rule of thumb calls for counterweights about 2/3 the actual load - that would put it at 30 pounds load and 20 pounds CW).
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Bob D
sage
Reged: 05/24/08
Loc: Dallas, Texas, USA
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Re: "smoothest guiding" mount for $2K, $3K, and $5K?
[Re: jrcrilly]
#3164303 - 06/15/09 04:42 PM
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The confusion you mention is unfortunate. The "not pushing it" load for the SXD must be greater than 20 pounds, though. The straight SXW is conservatively rated at 22 pounds for imaging (no derating required). The SXD is probably good for 30 pounds (which would make sense, as the usual rule of thumb calls for counterweights about 2/3 the actual load - that would put it at 30 pounds load and 20 pounds CW).
Perhaps the SXD is the "best compromise" for what I've been thinking about.
Does anyone have comparison experience with guided AP on an SXD vs. an Atlas or CGEM? Does the SXD have less of the "second-to-second jumpiness" which is harder to guide out? Also, does it seem that the higher price of the SXD is partly justified by better QC?
Note that I saw an excellent review of the SXD in Astronomy Technology Today a few months ago. I then joined the Vixen Sphinx Yahoo Group and saw a number of owners discussing "DEC noise, gear mesh", etc." problems. Of course, I know that you typically get more posts from the "unhappy," but I couldn't help but think that the Vixen QC might not be any better than the Synta.
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tim53
Postmaster
Reged: 12/17/04
Loc: Highland Park, CA
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Re: "smoothest guiding" mount for $2K, $3K, and $5K?
[Re: Bob D]
#3164371 - 06/15/09 05:16 PM
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but I couldn't help but think that the Vixen QC might not be any better than the Synta.
The QC might not be better, but the Q definitely still is. You seem to be most interested, in this thread, in finding a mount that can give you a smooth PE that will be easiest to guide out. The Vixen mounts are more likely to deliver this than the chinese imports (at least so far as I've known, though things are changing very rapidly these days!).
I recently upgraded an old Super Polaris mount with an iOptron Gotonova goto kit, and so far I'm pretty happy with the results (and it was CHEAP to do!). See
My thread on goto'ing a Super Polaris
I once compared the PE on all my mounts using Astro IIDC and a firewire camera. The results were interesting.
My old super polaris had a very smooth PE of about 20-22 arc seconds. So smooth that it was easy to take 2 minute unguided exposures with a 4.25" f/5.5 Newt and have more than half the frames suitable for stacking.
My ~1980 vintage C-8's spur gear drive was also around 20 arc seconds PE, but very jumpy and non-periodic. Too long a focal length to image unguided, so I never tried. But I did try once to image with an SBIG ST2000XM and an AO-7 (WAY out of balance, so I only shot toward the meridian and zenith during that test), and the AO-7 gave round stars in exposures about 5 minutes long. No guide port, though, so I haven't used the old fork mount since that experiment.
Tak EM-10, Temma 2 Jr: This is truly a wonderful "light to medium duty" mount. I routinely mount the C-8 on it with a Megrez 80mm piggyback and take astrophotos with it. PE tested out to right around 8-10 Seconds as advertised, and is very smooth.
Tak NJP Temma PC: Wonderful moderate-heavy AP mount. I bought mine used for about $4500 about 3 years ago (paid about $2200 for the EM-10 at the same time). This mount doesn't care about winds that often kick up at my dark sky site, though I've only taken dark sky images with short tubes, like the C-8 with various refractors piggyback or on a Triad bar. PE right around the advertised 4 second level, and very smooth.
I would think that a used Vixen mount, perhaps a GPDX or some other derivitave of the polaris, and perhaps with one of the modern goto upgrade kits, would not steer you wrong, though your 9.25" would be at the upper limit for comfortable AP.
-Tim.
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tim53
Postmaster
Reged: 12/17/04
Loc: Highland Park, CA
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Re: "smoothest guiding" mount for $2K, $3K, and $5K?
[Re: tim53]
#3164377 - 06/15/09 05:19 PM
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I forgot to add the Nexstar 9.25 GPS, which I also tested, though I think I mentioned this before: 20-22" PE, very jumpy. But autoguidable.
-Tim.
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adamsp123
scholastic sledgehammer
Reged: 11/20/08
Loc: welshpool mid wales UK
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Re: "smoothest guiding" mount for $2K, $3K, and $5K?
[Re: Bob D]
#3164496 - 06/15/09 06:30 PM
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Hi Bob.
OK I have a Vixen Sphinx mount,EQ6 and Atlux. The sphinx is very light but incredibly sturdy and will take quite a load,I have had a meade 10" SNT at 29lbs on it and worked fine, although in theory it would be overloaded, but it gave one minute unguided tracking without problem. The Starbook IMO is great to use and has an autoguiding port. The sphinx is heck of a mount.
I also have an EQ6 which is a much more massive beast which seems to be one of the main choices for astrophotographers in the UK as it offer incredible value for money and takes a high load.
I recently got my hands on a secondhand Vixen Atlux at a good price and that again is a real cracker oozes quality, so I am now selling my EQ6 but I would have happily stuck to the EQ6 but it was an oppotunity I couldn't miss.
I would recommend that you consider autoguiding right from the off because soon as you do, you will wonder why you didn't do it sooner.
Also the Sphinx SXD is worth a thought.
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Bob D
sage
Reged: 05/24/08
Loc: Dallas, Texas, USA
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Re: "smoothest guiding" mount for $2K, $3K, and $5K?
[Re: adamsp123]
#3164620 - 06/15/09 08:04 PM
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Thanks to a couple of Vixen mount owners for chiming in here to reassure me. I feel better already!
So, my current conclusions, based on the overall advice regarding my criteria for each rough price point (new) are:
(1) <$2K -- CGEM or Atlas
(2) <$3K -- Vixen Sphinx SXD
(3) <$5K -- Tak EM-200 (or EM-11)
Thanks again to all!
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Mark Jenkins
sage
Reged: 06/25/08
Loc: Wisconsin
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Re: "smoothest guiding" mount for $2K, $3K, and $5
[Re: Bob D]
#3164739 - 06/15/09 09:26 PM
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Tim!
In the Court of the Crimson King! Awesome!
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tim53
Postmaster
Reged: 12/17/04
Loc: Highland Park, CA
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Re: "smoothest guiding" mount for $2K, $3K, and $5
[Re: Mark Jenkins]
#3164798 - 06/15/09 10:02 PM
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Yes!
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