questions for any Vixen SXD or Losmandy GM8 users

[madtuna (Steve)]

Contemplating either mount and wieghing up the pros and cons.

Will be mounting either my Vixen VC200L (6 kg) or NA140SSF (6.5 kg) plus a 40D.
I'd love an Atlux or a G11, just cant justify the cost at this stage

Any input as to suitabilty as a portable but reasonable imaging mount appreciated.

also the difference between a SXD and the SXW??

many thanks

[[1ponders] (Paul)]

What will you be using for a guidescope? Imaging with a 40D at the long focal length of the VC200 is going to be pushing it for either of these mounts. Are you planning to focal reduce it?

As a portable mount the GM8 is still pretty weighty, but at least it will still be stable enough . I use my 8 with Orion ED80. a small 420mm refractor for a guidescope and my DSLR. Great little setup. Are you thinking Gemini controller or just the Digital Drive?

Can't comment on the SXD

[madtuna (Steve)]

oops, yep have the vixen focal reducer, for a guidescope I have a WO 66

and yep thinking of the Gemini

Thanks for your input...it all helps

[Ian Robinson]

Originally Posted by madtuna

Contemplating either mount and wieghing up the pros and cons.

Will be mounting either my Vixen VC200L (6 kg) or NA140SSF (6.5 kg) plus a 40D.
I'd love an Atlux or a G11, just cant justify the cost at this stage

Any input as to suitabilty as a portable but reasonable imaging mount appreciated.

also the difference between a SXD and the SXW??

many thanks

I considered Losmandy mounts and also at the SXD.

I'd spend a little more and get hold of the SXD rather than the SXW (the SXD is beefed up and has a pretty good load capability of 50lbs incl cws => Deluxe version: up to approx. 15kgs). You are better off having a GEM that is oversized (capacitywise) than one that is lighter.
You might not even need counterweights with the scopes you are talking about (and only very small ones for the side-by-side scopes arrangement when guiding with the SXD).

I've also read that drives on Losmandy's GEMS (the smaller ones and the G11) and are bit iffy if the scope is not properly balanced , that would worry me if I have a set up that has to be portable.

The 5 year warranty on Vixen is a big plus. Not sure what Losmandy offers (probably only 12 months).

GEMINI is a pretty expensive retrofit for Losmandy GEMS from what I recall .... that's a MINUS.

[madtuna (Steve)]

Thanks Ian!

[Ian Robinson]

Originally Posted by madtuna

Thanks Ian!

You're welcome .... I bought an Atlux BTW.

One other thing to consider : you wont always have the scopes you have now and will probably upgrade to something bigger eventually ... most of us do (a few times) , a more capable GEM than you really need now will save a lot of time and money later and if chosen wizely , will be something that might last a lifetime and see several OTA upgrades.

A lot of companies copy Vixen GEMs , for good reason , that is they set the pace and are benchmark setters.

[madtuna (Steve)]

yeah.. I will eventually end up with a G11..well that is my aim, but I also want a more portable, affordable smaller mount but still of good build quality and longevity, hence my looking at either the Vixen or GM8

[JohnG (John)]

Lets clear up a bit of the nonsense that is going around concerning the drives of Losmandy mounts.

I have both a GM-8 and a G-11 and the fact is, I have never had a drive problem. Drive problems that are reported are user caused and the main cause of that is balance or the ability of the user not to be able to balance their system in 2 axis or in the case of side by side mounting, 3 axis.

My GM-8 has the original stepper motors and the mount is some 9 years old now, I run an Argo Navis with DSC's, the stepper motors have significantly more torque than you will ever need and do indeed tolerate quite an amount of imbalance.

My G-11 is fitted with a Gemini unit, on the new mounts you have 2 options, either the standard servo motors or the new Maxxon high torque motors. Problems are caused by users not properly balancing the load, so a properly balanced load will have almost no effect on the drive motors, that said, the standard servo motors are more than up to the job with the mount properly balanced, the Maxxon motors are that much better.

As to your question, I have never used a Vixen mount so I can't comment, I have used the GM-8 and G-11 for a long time now and the GM-8 with the G-11 tripod carries my Takahashi TSA-102 as a field mount with absolutely no problems at all.

Cheers

JohnG

[Ian Robinson]

Hi JohnG,
A Takahashi TSA-102 is a very fine piece of kit , do you use it with a TOA Flattener - 35 and a TOA Reducer ?

Also a Takahashi TSA-102 OTA only weights 5 kg , so it is no wonder the G11 handles it "with absolutely no problems at all ". You are not exactly pushing the load limits of the mount or the motors with that.

Having to disassemble and reassemble the gear (in different configerations) if you can't have a permanently , or semipermanently , established rig is a real pain in the butt and (unless you are fastideous) getting the rig properly balanced (especially in 3 axes) it can be a real challenge .

Like I said , it's better to get a GEM that is oversized , which is what you have.

I rejected the G11 + Gemini in my decision for more reasons (of a technical nature) than those mentioned here , that doesn't mean it isn't a good GEM , just didn't make the cut (nor did the CG-E) when I was choosing. I also got a very deal on an Atlux which clinched it.

[JohnG (John)]

Hi

The G-11 is set up in an Observatory, the GM-8 is always being setup and pulled down again at various places, bounced around in the rear of my little FWD , my field mount.

Cheers

John G

[Omaroo (Chris Malikoff)]

Steve - you might also consider going straight to the G11 - but get the Digital Drive (vanilla) version. Save yourself a pile of money initially ($3.7k for the basic G11 vs. $4.2k for the GM8/Gemini), and then go for the Losmandy shaft encoders and an Argo Navis down the track. It's an option unless you really need GOTO for remote operation.

The new series of GM8's and G11's all use the new worm metallurgy anyway, so any misconceptions over their reliability are entirely moot. As John stated, badly balanced equipment will wear any drive system prematurely, Losmandy, Vixen or Paramount - it don't matter which.

[JohnG (John)]

Ummm, I don't see where I said the TSA-102 is mounted on the G-11, it is not, an FS-128 is mounted on the G-11. Until I got my ST4K the G-11 was carrying a Cassady Side by Side plate, heavy Losmandy dovetails, 12" Cassady saddles, a Cassady TGAD, SW SkyWatcher ED80 as a guidescope, a load which required 33lbs of counterweight, that had to be balanced .

The GM-8 on the otherhand is my field mount, something I quite clearly stated, I have absolutely no problems setting it up or tearing it down, something you get used too, in that matter, to each there own, it dosen't bother me.

Re the TSA, yes I do have the 35 Flattener, Reducer and the 1.6 extender, I use these with an unmodded 350D and plan to use the 35 Flattener with the SBig ST4000XCM when I can get 240v at a site.

Cheers

John G

[Ian Robinson]

I see.

You've got some nice OTAs and gear there.

Still the Takahashi FS-128 OTA only weighs 7.5kg (by itself) and is well inside the capabilities of a G11.

A SBig ST4000XCM would add more weight as would a guidescope (or is a 4000XCM self autoguiding ?).

[JohnG (John)]

So what is the point with the obession with OTA weights .

Obviously only part of what I said was read and understood. I will make it clear, for some 4 years my G-11 and Gemini, fitted with the standard Servo motors, carried in excess of 25 Kgs, on a mount rated at 30 Kgs, the rig was properly balanced and I had no problems with the drive motors, I also never had a problem with guiding. I have now gone to a Self Guided SBig camera, the weight is now down to around 12.5 Kgs.

My original imaging rig was in excess of the recommended 2/3rds rule for imaging, ie for imaging the load should not be in excess of 2/3rds the total carrying capacity of a given mount.

I fail to understand as to why reducing this load is such a problem, got to be less stress on the motors, so yes, the mount is well within capabilities, so what, it does what it is designed to do, it is not a Tak or AP, when it grows up, maybe, at the moment it does what I want it to do, no problems.

I think I will rely on my 40+ years in this hobby to make up my own mind, I'm outta here, got more important things to do.

Cheers

JohnG

[madtuna (Steve)]

Thanks Chris, and that's what I'll probably do. A good option though probably a bit dearer doing it that way than the whole G11 kit outright. I have a C11 which will end up fully loaded.

I also still want a good portable mount for my VC200L hence my quiery here

Originally Posted by Omaroo

Steve - you might also consider going straight to the G11 - but get the Digital Drive (vanilla) version. Save yourself a pile of money initially ($3.7k for the basic G11 vs. $4.2k for the GM8/Gemini), and then go for the Losmandy shaft encoders and an Argo Navis down the track. It's an option unless you really need GOTO for remote operation.

The new series of GM8's and G11's all use the new worm metallurgy anyway, so any misconceptions over their reliability are entirely moot. As John stated, badly balanced equipment will wear any drive system prematurely, Losmandy, Vixen or Paramount - it don't matter which.

[JohnH]

Hi Steve, I have a VC200L and WO66 on an SXW mount. I have the Vixen FR and a Canon20D that I use at prime on either scope with a QHY5 (mono) guidecam on the other. This setup works pretty well and is portable, the SXW mount is very good mechanically and the Starbook has evolved into a good unit with support for autoguiding and PEC. Imaging at F9 is in fact doable with this mount but in my case the 0.7" per pixel image scale is wasted effort due to the seeing - so I run with the FR in most of the time.

The main issue I face with the SXW mount is DEC backlash which is large but mostly can be avoided with careful balance and guide software configuaration. I agree with the previous posterd about the newer SXD - I think that mount would be significantly better than the SXW for the load however there seem to be a few issues with the relevant Starbook firmware atm. The SXD seems to need v40 (as does the new Atlux) and this in turn has a few issues, mostly users complain about noise. Vixen also seem to send out these mounts very tight so it may be best to ask your supplier to assemble and adjust and demonstrate the mount before you accept delivery if you go the SXD route.

PM me if you have any questions and have a look at:

http://groups.yahoo.com/group/Vixen_...?yguid=7983213

[madtuna (Steve)]

Thanks John! that helps

[astronomer2002 (Ian)]

I was looking to upgrade my portable imaging setup and couldn't decide between the SX and the GM8 - so I purchased both s/h, with the intention of selling one later.

I have used a SP with modified controller to take guided images sucessfully in the past, but I wanted something I could use with up to 1000mm efective focal length and the drives of my old SP are just not up to that.

Having a G11 already (just too heavy to be portable) I expected the GM8 to be good, but I could not justify the huge additional cost of the Gemini system so I wondered whether a SXW would fit the bill. If you want to maximise your imaging time then GOTO is almost essential. I reckon I wasted several hours a night when on hol in the southern hemisphere with the SP tracking down objects and then swapping the eyepiece for a camera once I had found the object.

As expected the GM8 works brilliantly. The build quality is good, the drives are excellent and the polar finder (I don't have one on the G11 which is permanently mounted) is a revalation - it takes 2 mins to get the mount on the pole. I cannot speak too highly of this scope - it is far the best I have ever used. The downside of the mount is, of course, the weight. The GM8 is far too heavy to contemplate taking on flights abroad.

When the SXW arrived the difference in quality was startling. Balance with any load was not a problem - in fact you couldn't balance it! The shafts were so tightly gripped that a fs102 could be held in place without a counterbalance weight! So I stripped it down to establish what the problem was. Joining the SX group told me this is a common problem if not a universal one. Smells like zero quality control to me. I was not impressed by the slop in the gears and read that I could expect changing direction in dec could require the motor to be run for several seconds. No matter what I did with the dec drive I could not get this below 4 seconds at guide speed. This is just rubbish design I am afraid. There are too many gears in the drive chain.

Now for the mount in use. I found the SX polar finder almost inexplicable and very fiddly in the dalight. It is quite impossible to use (as intended) in the field. In the end it is quicker to use it like the old faithful SP polar finder and ignore the many concentric wheels you are supposed to align.

Once on the pole I found the alignment setup a bit odd - but ok. The good news is that the GOTO works fine. When I tried taking images it soon became apparent that the time spent on getting the mount well aligned to the pole had been wasted. Only by offsetting the mount from the pole to make sure the dec guiding direction didn't change during an exposure could I get anything approaching round stars.

After using the SX for a couple of months I can honestly say the simpler SP is just as good an imaging platform - if you are using an autoguider, that is.

If I had not already had other mounts to compare it with I might have concluded the SX was an acceptable platform as I have been able to achieve 5 minute exposures that have yielded round stars (albeit with focal lengths of 500mm or less) However, I believe the hype about this mount disguises some basic mechanical flaws and poor quality control. I recomend anyone contemplating a SXW/D mount should read the postings on the SX yahoo group. If you want a compact portable mount for visual use they perform well enough, especially once you get to grips with the Starbook.

The one thing the SXW mount has done is make me somewhat less critical of my old LX200 mount as an imaging platform