After much research on a good photography mount, I've 99% decided on a Losmandy GM-8. 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??
Hi Lee, I have both the 8 and the 11, both working with the ArgoNavis (when I fell like swapping the encoders over ). 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.
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.
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.
Not at all, balance is the key here. Finding a counter weight small enough is the hard part I've run my G11 and GM8 with a tiny 60mm carton refractor side by side with 300D with np.
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???
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...
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.
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.
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.
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,). 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.
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.....
GM-8 advice please
I have a question for those in the know:
![[1ponders]'s Avatar](../vbiis/customavatars/avatar45_9.gif){kind=avatar}
). 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.
