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GEM for f/9 4" refractor?

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#1 Dragonwatcher

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Posted 11 June 2009 - 07:12 PM

I am about to take the plunge for a GEM for my Celestron C102F 4" refractor. I am looking for the least expensive and least heavy equatorial mount I can get that still will give me great stability even when binoviewing. I don't want "the best". I don't want much overkill. I am looking to get a very solid & very competent mount & tripod.

I am thinking possibly an Orion Skyview Pro, and I actually have an offer for an older one, but it has the thinner 1.5" tripod legs rather than the more robust 1.75". Is this likely to work well for up to 13-14 pounds? Are there better options in the same range? Are manual slo-mo controls easy enough to use that motors are luxury items or would I likely regret not getting motors?

I should state my needs are solely visual and I will rarely be much over 200X. I just want to be able to track the moon and planets. I will probably use my alt-az Giro mostly but would like a GEM for Saturn and Jupiter extended viewing.


Open to any input from experienced GEM users with longish 4" refractor setups, now or in the past. Again, thinking cheap & competent rather than pricey and wow.

#2 Tom and Beth

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Posted 11 June 2009 - 07:39 PM

I've used a Vixen SP for my TV-102 and 4 inch Vexin F9.8
it "kinda" did the trick. Relatively stable and all that.

but

There really is no substitute for a SOLID mount that doesn't jiggle every time you touch the focus or align the finder. Guess you can say I've become spoiled, and so I'd recommend a G-11 class mount or better. It'll grow with you as your interest grows.

Did I mention I hate cheap shaky mounts?

#3 Dragonwatcher

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Posted 11 June 2009 - 08:28 PM

Tom and Beth,

I do understand what you are saying, and that's advice that I would hope to follow in the future. HOWEVER, at this point and given my finances, the choice is simple: good, solid & inexpensive (under $300 used) or NOTHING.

My most pressing concern: should I pass on the SVP with the smaller legs or would it suffice for a telescope of my size? I have been made an excellent offer, but it would not be a bargain if it wouldn't work well for my Celestron C102F. Should I hold out for one with larger legs or go with something else that would work better within my parameters?

#4 GShaffer

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Posted 11 June 2009 - 08:29 PM

I am going to say find a nice used GM-8 Losmandy. I have one that I use for trip to the darksite mount which I mount a Vixen ED102SS and occasionally its F/9.0 brother the ED102S which is roughly the same scope you have. For visual only it would be fine with yours......and is a great little mount that makes me think ferrari testarosa for some inexplicable reason (it looks good:).....Just put a G11 saddle on it for greater stability with the longer OTA.

Not as an inexpensive route compared to some but if you are going used anyway then consider you can buy parts and fix it yourself rather than have to ship the whole thing to repair to get it fixed. I kinda like mine if you cant tell :)

Greg

#5 Eddgie

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Posted 11 June 2009 - 08:32 PM

Least expensive and least heavy.. Well, to get a light mount that is stable, to me you are talking Vixen GP with Vixen HAL 130 legs. But this is not cheap. The HALs are far lighter than the steel legs and stiffer than the AL130 legs. But these tripods are not cheap.

I used a CG5 Go-to over a Vixen HAL 110 to carry a Vixen 140. Not super stable, but quite good for visual observing and it is really astonishing how light the HAL 110 Tripod is. The HAL 130 weighs just a bit more.

The steel legs are a bit stiffer than the HAL 130s, but of course the LXD75 and CG5 Go-to mounts now come with those, and you can pick up the whole mount for $4 to 450 these days. Either will be fine for a 4".

The elegant option is a Super Polaris with wooden legs the 9 volt battery in the handset. These are beautiful mounts. The wood legs are stiff and light. The 9 vdc battery will run the mount in RA for hours. But these are hard to find.

I highly recommend the RA drive. The Dec drive is not at all necessary because the Dec slow motion control is always just under the the end of the telescope. YOu use the handset for slight tweaks in RA, and the slow motion for slight tweaks in Dec.

I have an older Polaris (not Super Polaris) with the 9VDC RA drive and a set of Vixen HAL 110 legs. Love it. Can even be used in Alt Az mode. Ah, but it is maybe just a little light for a 4" refractor (though it used to be sold with a 114 reflector on it). Anyway, it is super-light weight. I can carry the mount with a C5 on it with the power supply, counterweight, and all the eyepieces in one trip. Could not do this with a 4" refractor, but just giving you an idea of how light everything can be.

So, Polaris on wooden legs with RA drive would be a sweet setup for a C102F.

Or a more expensive option would be a GP with HAL 130 legs.. A classy mount and BEAUTIFUL for the telescope if it is the older green trim.

#6 Dragonwatcher

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Posted 11 June 2009 - 08:50 PM

GM-8 may be in my future but not my here-and-now. I don't think they can be had for less than a $1000.

Polaris might be an option, though sounds like I would be on the cusp of weight with my refractor, especially if loaded with binoviewer and 2 EPs.

I don't hear any love for the Orion SVP at this point...

#7 hudson_yak

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Posted 11 June 2009 - 09:18 PM

I think the SVP is adequate for my F9 scope, though just barely. And it's the newer model with the 1.75" legs, and I only go to 150X with it. Binoviewing at heigher powers, not so sure.

I have all the motor options for it: TrueTrack, SynScan GoTo, none of them are without annoyances in operation and I swap them in and out frequently. Currently using it with no motors, though that isn't going to last long either. I don't see any other variants as having any better solutions, though, they all work the same, operationally (the infernal clutch for tracking drive, heavy power supply and lots of keypresses to get tracking with the GoTo system). Losmandy is one with a good alternative approach for this, but I was never able to justify the cost, especially not being convinced I wasn't going to want some form of manual slo-mo control after living with it for awhile.

The only addition to my SVP that's been a complete success is a flex control stalk for the Dec.

For stability, I think the SVP with a strong wooden tripod ought to be pretty good.

Mike

#8 Dragonwatcher

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Posted 11 June 2009 - 09:28 PM

Mike,

Thanks. A bit depressing... but thanks. I guess one makes do with what one can afford. I want a Ferrari, but my Subaru works.

#9 KWB

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Posted 11 June 2009 - 10:31 PM

Hello Jackie

A non-GOTO CG5 was plenty stable for my 4 inch F/9.8. The slow motion controls are a must for me. I can do without a tracking mount but not micro controls. Keep looking and you'll find a used one in your price range. You will then have a very nice to use setup with that sweet refractor.

Good luck :waytogo:

#10 Dragonwatcher

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Posted 11 June 2009 - 10:58 PM

Kenny, I am assuming you mean you can do without a motorized tracking mount that finds an object for you? I have slow motion controls on my alt-az Voyager, but I have to fiddle with both to keep Saturn in view. With a non-motorized GEM, as I understand it, I get it polar aligned, find my planet, and then by simply using ONE RA slo-mo knob or cable I can track the planet. So manual tracking is much simpler. It I have a RA motor, then the planet is kept in view without needing to be manually tweaked. If it has GoTo, then after a polar and star alignment, I can punch in the numbers for Saturn, it will slew to it and track it.

Have I got the distinctions correct?

I know there is a nice CG-5 for sale about an hours drive from me, but so far the price is a bit too high. I do see them in my price range occasionally, so it is good to know they are good options.

I think the CG-5 and Orion SVP are meant as competitors. Are they comparable quality? Or is one superior? Anyone with an opinion based on first hand experience with both?

#11 KWB

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Posted 11 June 2009 - 11:17 PM

Your distinctions are correct. Other than cosmetic differences the CG5 and the SVP are the same basic mount,both with a theoretic weight capacity of 20 pounds. Not with a larger aperture,longer focal length refractor but for visual purposes either will support that 8 pound OTA of yours IME,even with a 50mm finderscope and a Hyperion sized eyepiece. My former 4 inch Celestron OTA weighed 8 pounds as well.

#12 Dragonwatcher

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Posted 11 June 2009 - 11:47 PM

Kenny,

Thanks. That helps clear a bit of the fog out of my cranium.

#13 hudson_yak

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Posted 12 June 2009 - 08:46 AM

Looking at the two mount heads they seem like they should be similar in load carrying, though recent CG-5's come with a 2"-diameter tripod, making a big difference. The SVP has a rather unique rounded "style" to it that sets it apart, for good or bad, depending on your own sense of things, from most of the others.

I tried using a flex stalk for manual RA tracking but didn't find that very useable, it's easier to rest one's hand on the mount than hold it up all by yourself to reach the flex stalk knob.

I really dislike the clutch that comes with the RA tracking motor. I keep studying it to come up with some way to make it better. I've been spoiled from many years with my LX10 where one does not have to disengage tracking to turn the manual slo-mo control. Why this was not a design requirement for Vixen-type GEMs from day 1 I'll never know.

Mike

#14 GShaffer

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Posted 12 June 2009 - 09:02 AM

Just an FYI, a search of Amart reveals a number of GM-8's that have sold for well under $1000.....$750 and up.

GM-8 may be in my future but not my here-and-now. I don't think they can be had for less than a $1000.

Polaris might be an option, though sounds like I would be on the cusp of weight with my refractor, especially if loaded with binoviewer and 2 EPs.

I don't hear any love for the Orion SVP at this point...



#15 Dragonwatcher

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Posted 12 June 2009 - 12:59 PM

Greg,

You may be right, but the cheapest I saw recently was $850 PLUS shipping and everything else was $1000 or more. I did see that $750 offering - but the seller is in the Netherlands, and the mount is shipping from the American Virgin islands.Buyer pays shipping! That will be a BIG shipping bill...

But even $750 is beyond what I can justify right now. I do understand what you are saying, that a good quality mount is a wise investment long-term. I know you can ruin a good telescope with a shoddy mount. It's just a matter of practical economics for me at this point, though I do hope to one day upgrade.

#16 Dragonwatcher

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Posted 12 June 2009 - 01:07 PM

Mike,

I am intrigued by your LX10 remark on disengaging gears. Does that mean that any SVP or CG5 that has motors must be disengaged before using the slo-mo controls? Are there any mounts that I could get in the same general price range of these two suitable for a f/9 refractor that automatically disengage when manually nudged? Anyone can answer...

#17 Eddgie

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Posted 12 June 2009 - 01:31 PM

Post deleted by Eddgie

#18 hudson_yak

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Posted 12 June 2009 - 01:36 PM

From what I have seen, these types of mounts (Vixen and clones), when equipped with non-GoTo drive systems (eg. Orion TrueTrack), require disengagement of a drive clutch to turn the slo-mo control knobs. Vixen even makes the drive clutch an extra-cost option (Orion includes it as part of the TrueTrack packages).

In theory, to avoid messing with the clutch you'd just use the hand controller to run the motors to center the object, for Orion though the max speed is 8x, rather painfully slow. Vixen does have 32x for this on recent mounts, which is good enough, but you probably won't find one in the price range you are hoping for. Motor systems for Vixen are really expensive, so there don't seem to be many available used.

The GoTo systems for the mounts don't even offer drive clutches. They do offer fast-enough centering speeds with the hand controller though.

All these mounts can be pushed-to while tracking by disengaging the axis locks. In this way they can be operated just like the Losmandy mounts, however, there'll likely be more stiction than Losmandys have (since those were designed with clutches meant for just for this usage) making centering at high powers not much fun. I've tried to use my SVP this way but it quickly becomes annoying. It really needs the slo-mo controls. The Losmandy drive system offers a 16x speed that goes to 32x after a couple seconds I believe, so that should work pretty well too, for those times when push-to centering is not getting it done easily enough.

The old-fashioned SCT wedged-fork tracking systems decided early on to provide two nested gear rings in the base, one for the drive pinion/worm, the other for the manual slo-mo pinion. Unfortunately Vixen did not go this way. Wish they had. Their drive systems look an awful lot like an afterthought, and of course the clones just went with it.

I like my SVP the best with no motors at all, I seem to come in from a viewing session least annoyed when it's set up that way. It has the further advantage of looking better without the motor drive cover in place, a quite ugly box-like plastic appendage on all these types of mounts, even Vixen.

Mike

#19 Eddgie

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Posted 12 June 2009 - 02:08 PM

Yes, I would go so far as to say that the "Clutches" on the CG5 style mount aren't clutches at all. They are Axis "Clamps" according to the Vixen manual.. They were not really designed as clutchs.

I wrote a couple of responses before I caught a followup post from the OP that said he was looking to keep it under $300..

Based on that, I would say "Good Luck." I still think the best deal in a used mount would be an older SP or GP because these are really excellent mounts, with true Slow Motion (though again, the Vixen Slow Mo doesn't work in RA until you undo the drive clutch).

Otherwise, the only real choice here will be used CG5 or clone.

If I were limited to only $300, I would go with an LXD55. They are a bit shaky, but you can stiffen them up, and while they don't have mecanical slow motion, if you don't mind having to power it, you can at least get a bunch of electronic slow motoin speeds.

This is actually the kind of mount I use on my TV 101. Not the most stable mount in the world, but since you don't ever have to touch it for sweeping and slewing, it works well enough, and you can buy a used LXD55 for less than a Vixen GP (though it is not as sturgy).. And in fact, I sold the Vixen GP to go to a small Go-To.. So that should say SOMETHING.

But some people don't want to mess with power cords or even limited setup. They just want to plop and go. Though you can have an LXD running in less than a minute, many people don't want to mess with it.

Me? I found having the electronic motors for slow motion to be 50 times better than messing with clutches and worring about balance.

I LIKE my LXD55. These mounts get little respect because people think you have to "Super-charge" them or whatever it is called. I picked up mine used for less than $300 and I think it represents one of the most outlandish bargians in used equipment.. Heck the PARTS are worth more than that! LOL.

#20 Eddgie

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Posted 12 June 2009 - 02:09 PM

Just so the message doesn't get lost in the long response above...

For $300, there is only one choice.. LXD55.

#21 GShaffer

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Posted 12 June 2009 - 02:23 PM

I missed where he said under $300.....given that restriction I have to agree with you. Though one might get lucky and find a LXD75 for close to that. Either can be easily adapted to an LX200 tripod when its standard tripod just wont serve due to the shakes also.....

Just so the message doesn't get lost in the long response above...

For $300, there is only one choice.. LXD55.



#22 Dragonwatcher

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Posted 12 June 2009 - 03:41 PM

Thanks Mike, Greg, Eddgie and Kenny. I've learned a lot... Appreciate your taking the time to share your thoughts with me.

#23 KWB

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Posted 12 June 2009 - 03:57 PM

It's been my pleasure to share a little of my experience with you,Jackie. Let us know when you get your mount. :)

#24 2682

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Posted 13 June 2009 - 01:31 PM

I was going to suggest the CG-4, but the weight of the binoviewer and 2 EP's may be too much.
It's a shame you can't spring $600 for a new LXD-75 or CG-5. I do not think you are likely to get something acceptable for $300. Maybe you should wait and accumulate some more money.

#25 jsiska

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Posted 13 June 2009 - 02:43 PM

The C102F were originally sold with a Vixen Super Polaris mount with ash wood legs. They are still nice mounts and usually the asking prices on the astro classifieds are between $300 and $350 with manual fine adjustment knobs or cables. If you can get one with a half pier you wont have to extend the wooden tripod legs much for better stability at observing heights. SP mounts will probably never sell for much lower in price so if you keep in good shape you can sell it for what you paid for it when you decide to move up. The only thing is that if and when you move up, you may decide just to keep the SP because it is fairly light weight and easy to move.

Jim






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