GM-8 advice please

[Lee]

After much research on a good photography mount, I've 99% decided on a Losmandy GM-8. :D I have a question for those in the know:

The Gemini costs about $1400 extra at purchase - will I regret not getting it at initial purchase, and end up getting it later???
The main thing I'd like about Gemini is PEC, rather than GOTO... are there other advantages of Geminin I'll end up wanting for??

TIA for any help guys..... :)

[[1ponders]]

Hi Lee, I have both the 8 and the 11, both working with the ArgoNavis (when I fell like swapping the encoders over :P ). I do however regularly use a G11 with the Gemini and unless you are thinking of getting encolders and and AN then the Gemini is the way to go. Each has its pros and cons. If I was just doing visual work then I'd definately go for the AN. For imaging though I'd get the Gemini.

If you decide not to get the gemini then you will still need to get some form of communication between your mount and computer to autoguide. So the long and the short is if you can afford it, then go the gemini first up.

[Lee]

Thanks Paul - Is your recommendation of Gemini for imaging to do with Autoguiding mainly - or PEC, or something else??

[JohnG]

Hi Lee

You mentioned that you will using a GM-8 for photography, a couple of things to take into consideration here. Do you know the all up weight of the equipment you intend to use on the mount, ie: OTA, camera, quidescope, rings etc. The GM-8 has a load capacity of about 15Kgs/30lbs, the normal consideration is that the weight of all your gear should not exceed 2/3rds the carrying capacity of the mount. The weak point of the GM-8 is the tripod, whilst sufficient for normal viewing, IMO it lacks when used for photographic work.

All new GM-8s and G-11s now have the high precission worm so PE is not a major problem as it used to be, the latest Gemini system is Level 4.02 and the PEC apparently works well together with other fixes.

I have both a GM-8 which I use as a grab and go mount, no Gemini or DSCs and a G-11 with Gemini, this is permanently mounted and used for photography, being guided with an ST-4. I have had no problems at all with either mount or the Gemini system as such although there is a steep learning curve. You will probably have to learn how to make adjustments of the mount but they are simple to work on.

My advice would be to save a little longer and get the G-11 if you can afford it, the payload is double, 30Kg/60lb and in the field you can kick the tripod and it will not move, absolutely stable. The other thing is to think about the future, do you intend to upgrade equipment etc.

Cheers

JohnG :thumbsup:

[Striker]

Lee...what scope are you putting on the G8...what will you be imaging and with what camera.

With my G11/Gemini I have yet to do any pec training imaging at 2500mm...

Something I will endeavour to do soon though.

[Lee]

The imaging load at most would be an ED80 with a D70 hanging off it's tail, and a cheapish achromat to guide through.

Will have a look at the G11, but feel the 8 would be sufficient to keep me happy for a fair while!

[gbeal]

The GM-8 is a very good mount, but if you progress like nearly eveyone I have seen with a GM8 (me included) the G-11 will soon beckon.
Unless you know for sure you will never progress, or have a very good and very cheap GM8 immediately available, then my money is on the G-11, sorry.

[[1ponders]]

I know it is way overkill, but I find having both a real advantage at times.


Just a thought to work towards ;)

[Lee]

My partner and I were talking about that yesterday - how we'll have to compete for Losmandy time! Maybe the 8 now and an 11 for xmas? :D

Do these suffer if you are way under the load limit - like the EQ6 is rumoured to do???

[[1ponders]]

Not at all, balance is the key here. Finding a counter weight small enough is the hard part :P I've run my G11 and GM8 with a tiny 60mm carton refractor side by side with 300D with np.

[Lee]

Great guys..... Problem is, before I had two choices to ponder.... now I have four delectable choices! Talk about spending a tax cheque before you get it... ;)

I see the motors are changed with the Gemini upgrade - does this offer specific advantages???

[Garyh]

Hi lee,
I decided myself to go for the gm-8.. being more portable and conveniant to setup if you have to travel and my load would be about 10kgs max and as I don`t plan on anything bigger for a while shall give me a few years service.
I plan to have my 6" astrocam (still under construction) with 70mm guidescope plus camera etc which comes to nearly 10kgs or my old genesis and addons which comes to 7.5kgs. Seen someone with 8" GSO plus extras...etc on a gm-8 and they were still happy with tracking etc..
If you plan on mounting it permanently and have the Dough go for the gm-11 but our budget only allowed for a gm-8 but I am still very happy to be getting a real mount...:)

[JohnG]

The motors on the standard GM-8 and G-11 are stepper motors, with the Gemini they are servo motors with an optical disc attached so the Gemini can read it's location in the sky and GOTO other objects, they also have a different gearbox. Stepper motors can only read their location in the sky if they are fitted with Digital Setting Circles (DSC) and go through an Argo Navis or similar.

If you are not aware, the GM-8 now comes with a 'D' series saddle, this makes GM-8, G-11 and Titan all compatable and so allow the interchange of OTA's without changing Dovetail Plates.

Cheers

JohnG

[rogerg]

Hmm, the debate of GM-8 vs G-11.

When I was looking for a new portable mount I chose the GM-8 then was recommended strongly to get the G-11. I'm very glad I didn't:

1) my load is a WO Megrez 80, Skywatcher 70x700 and 350D camera. This is all so under-weight for the mount that I only have the standard counterweight about 4 inches from the top of the shaft.

2) I have since seen a G-11 in person and was surpsied at the size difference. I consdier the GM-8 much more portable - tripod, mount, everything. But then I do have tight space limitations in my car (scope + camping gear + girlfriend doesn't leave a lot of room for a big mount!)

3) The GM-8 has great tracking capabilities and is easy to setup, easy to polar align, etc. There's nothing wrong with it's photographic capabilities.

I have used a WO FLT 110 on my GM-8 and was surprised to find it handled the weight (with 350D and counterweight fully extended) no problem. However if I was planning on a larger scope I would have chosen the G-11.

I have also used my GM-8 with the combination of WO Megrez 80, Orion 80ED and 350D piggyback, with naglers in both scopes. Again well under the weight limit and easily handled by the mount.

It all comes down to what you put on it, but if all you're going to put on it is a 80ED, camera and guide scope, the mount is going to laugh at it, really. And you'll enjoy the smaller (more portable) mount.

That's my personal opinnion :)

Roger.

[[1ponders]]

Seriously though, the reason I still have the GM8 is that I couldn't part with it. As others have said, it is a great mount. Yes the tripod could be a bit more solid, and no it won't handle 30 Kg, but you will be surprised at what it will carry.

Before I bought the G11 I had an 8" meade SCT plus 80ED, finderscope for each, plus 300D, and Losmandy guide rings. Add to that the side by side plate I made up with 2 losmandy saddles and a dovetail bar. Total weight was pretty damn close to the limit if not over it. Did it worry the GM8. Not in the slightest. Here is an image taken with exactly that setup. (http://www.iceinspace.com.au/forum/attachment.php?attachmentid=3322&d=1122731817)

[Striker]

It's upside down Paul...lol

Lee I didn't mean to purchase the G11 over a G8 more alongs the line's off I wouldn't being making my decision just on the gemini PE training.

How about the vixen Spinx has that entered the equation. Or even the HEQ5...it all depends on what you want to put onto it.

Allan gave the HEQ5 Pro mount a very good wrap.....I'm even thinking about one of these for a travel set up.

[JohnG]

Attached is a couple of photo's of my GM-8 when it was permanently mounted before I got my G-11, it handled this setup with ease.

Cheers

JohnG

PS: That is 2, 11lb weights as well

[[1ponders]]

Only from your perspective Tony ;)

I guess what helped my setup Lee is the compactness of the SCT, lever arm moment is minimal compared to a newt or even a f/8 refractor. Weight is not the whole story. I used, and still do, a side by side setup very similar to Johns (see link (http://www.iceinspace.com.au/forum/attachment.php?attachmentid=4002&d=1125386009),). That helps alot keeping the center of gravity as close to the mount head as possible, rather than piggybacking the guidescope. Normally my SCT would be where the Celestron 102-HD is.

[Lee]

Thanks for all the great advice guys.
Have been talking to my partner about the four choices GM-8/11 +/- Gemini, and she made the decision for us - just get the 11 + Gemini.
I'm starting to like the idea of a big newt on top for visual use (or maybe imaging once I gain experience) in place of the dob. An ED80 on this thing will look like a pimple won't it!
Might have to work a few weekends.....
Thanks again, will keep you all posted.....

[Striker]

Go for the titan if you have her saying yes...see how much you can get out of her...lol

[[1ponders]]

Good onya Lee. It's a big choice, but I don't think you will regret it. I know I didn't. Even though I'm still glad I have kept the GM8.

When you need some ideas on how to go about carrying the damn thing, give us a yell again ;) :lol:

[Lee]

Steady on.... thought I'd have a crack at a Tak first! hehe ;)

[Lee]

Thanks again for everyones help so far....

Something else - what accessories should I get while I'm rattling the piggybank (throttling it I suppose!)?

What will I need to mount an ED80? what about piggybacking the D70?

[Panotaker]

I started out with a plain G-11 just with the manual setting circles. I then got digital setting circles and used it like that for a while. I then got lucky and bought a used Gemini setup and installed that. I was mainly using the mount with an 11" SCT. I couldn't really find anything with the manual setting circles with the 11". It got close, but at that focal length, it was pretty tough. I then put on the DSC's and it got easier, but with the mirror flop on the SCT, it still wasn't good enough. What I ended up doing was putting a TV-85 piggyback on the SCT and using that as a giant finder. That worked out well, since the refractor had no mirror flop, it would put everything just about dead center. I then switched over to the Gemini and that is really accurate. I mainly use it now for astrophotography with a 5" APO and it puts everything on my CCD chip. The nice thing about the Gemini is the Polar Axis Correction feature that gives me just about a perfect polar alignment.

It is true that you save $500 by buying the Gemini with the mount, but if you buy it seperate, you get to keep the old motors and controller which will come in handy in case your Gemini goes bad and needs to be fixed. I have kept my old motors as a back up, but so far have not needed them.

My other mount is a GP/DX with the Skysensor 2000PC. If I was going to get a small mount, I would get the GP/DX over the GM-8. The GP/DX tracks like a dream and the controller is a lot better than the Gemini. The only thing the Gemini beats it on is the Polar Axis Correction. But all these mounts are so expensive that you might as well just save a few more dollars and get the G11/Gemini. You will eventually put a bigger scope on it. It is not that much harder to setup, the pieces are just a little bigger and a little heavier, but it takes me just as much time to setup either one. For visual, my GP/DX will handle the C11 just fine, it just needs a ton of counter weight.

I normally leave the G11 tripod setup in the house with one leg loose. To bring it outside, I take off the loose leg and carry the tripod setup with two legs on it and then just put the third leg on which saves a lot of time in setting it up. I leave the 22lbs counter weight outside so I don't have to carry that every time. I built an observatory last year and the G11 is in there all the time now http://www.pbase.com/panotaker/absurdvatory

Ralph

[JohnG]

Congrats on the decision, I am sure you won't regret it, you will be getting a big, black, mean looking mount. lol

To mount an ED80, you will probably be looking at the DUP dovetail plate and a set of rings, be they the original rings that came with the scope or possibly a set of Parallax Rings with another DUP above so you can slide on a guidescope etc, that would be the way I would go.

Check out the Losmandy web site for a complete list of parts.

Enjoy.

Cheers

JohnG :thumbsup:

[Lee]

:thanks: Thanks again to everyone who helped me with this decision....

I've ordered a G-11 Gemini today. Now to wait, hopefully "only" 6-7 weeks.... I'm not very patient when it comes to things like this, so it will be a tough wait.
Just waiting for the pitter patter of little G-11 feet - actually would be more like the rumbling, ground shaking thuds akin to the Jurassic Park T-Rex I think......

[[1ponders]]

:cool: Congrats Lee Woo Hoo!!!!! Excellent. :D

Is it coming in from OS or did you buy here in Aus.

[iceman]

.. and how much was it in total (including shipping)?

[[1ponders]]

You'll have to pop up here to Qld so I can show you how to set it up, build a pointing model and do all those other Losmandy techi things that you will read about in the manual.

Oh and now you will need a few extra dovetail plates, guide rings (at least 2 sets) , side by side saddle mount, 3 axle camera mount, keep an eye out for a GM-8 to complete the set (you don't know anyone with a cheap second hand Atlas mount do you :lol: ) etc etc :D It is a status symbol you know and there are now certain standards to be kept :lol:

[Lee]

I know this is just the beginning of a big spend..... and the tax cheque isn't even here yet!

Bought here - ATS in Sydney, out of two retailers gave me the best "vibe" - another retailer stopped answering their phone after I asked them to check availability for an order, and doesn't answer emails either - hardly good business practice for a mail-order business I think.... he must already have enough money! :shrug: Anyway, I shouldn't have to chase a seller that much for a good sale like a G11.

Mike - $5400 - no shipping, I'll pick it up when it comes in. More expensive than another, but seems to have much better after sales support etc etc

Am hoping to get to Kulnura one of these days too..... need to put 3D people to these personalities :P

[Lee]

One other thing - has anyone heard much about the Swiss Maxon (sp?) motors offered now as an option by Losmandy - they apparently produce much better torque at 12V than the normal ones....?????
At an extra A$300 it isn't super expensive, but I assume the normal motors have performed well over the years now, wonder if anyone knows anything about them......

[allan gould]

There has been a lot of dicussion about motor burn outs with the losmandy gemini setup in the last year or so (see the yahoo site for this). Probably that is why they are offering the newer motors. But I have NEVER had any problem with my motors since I've had the gemini setup.
Allan

[JohnG]

The motor burnouts mentioned by Allan are almost exclusively caused by balance problems and operator error also a lack of understanding how the mount works. The Gemini is very sensitive to balance so make sure you spend a fair amount of time on it to get it right. I have never had any problems during the last 5 years I have had a Gemini.

JohnG

[Lee]

How does everyone power the mount? I've been told you need 13.8V DC @ 3A - pretty hefty power pack.... I figure the most economical and simplest to travel with (probably only option to travel with) is a deep-cycle car battery.

How does a car battery go? How long should I expect from different size batteries??

[Lee]

Update: as already posted in General Chat - G11 has touched down (a few weeks early too :party::cool: :party:)

my questions about powering in the post before this? any hints/advice/suggestions would be very much appreciated.... cheers!

[Panotaker]

I power my G11 in the field with a deepcycle 55 amp hour sealed gel sell. Mainly because I do photography and need all that extra power for cameras and computer. At home I have a 3 amp 12 volt converter or you can use one of those car jump starter thingies.
Ralph