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Hi, ?

First post here so glad to meet anyone. ?I recently got a GM8 and it looks to be in pretty good condition. It has the digital drive 492 on it currently and I want to upgrade to Gem 2 for the go-to and potential tracking it provides as my interest in AP may grow. ?This is my first Losmandy mount after lusting after them for some time. ?The question is, when I send out in for a full Gem 2 upgrade will that include any kind of lube, clean or inspection as the upgrade is done? I ask because I am going to order the services so I can get a date at least to get the work done through Losmandy site. ?I hope the question is clear, if not any help is appreciated for sure. Thank you and I look forward to many different topics as time goes on and I learn more about the mount!!

Craig H

Hi Craig.? Are you planning on a tucked motor/spring-loaded worm upgrade as well?? If not, you can just get the Gemini retrofit kit and install it yourself (this is what I did many years ago on my G11).? But keep in mind the cost of a brand new GM8 with everything mentioned is $2145 (mount head only).? The Gemini retrofit is $1595, and I suspect the tucked motor/spring-loaded worm upgrade in addition would put you well over the cost of a brand new mount.? Food for thought.

Keith

Craig,

You are in an in-between situation like Keith has said. Do you want to pay to refurb an older mount or put the same money into a brand new one? Not considering the drive system, you probably want to put in new bearings and perhaps new high-precision worm gears as well. That may amount to 300-500$ in parts if you want to do it yourself. Not sure what Losmandy charges for that service, but you would need to contact them. If you are handy, we might be able to help you redo and relube the main mount body. Perhaps you can get it operational as is, but fewer are still using the 492 that have reported in here. You might be able to find a used Gemini 1 or Gemini 2 system and retrofit yourself. Some guys are now adding the OnStep control system (which has its own forum) which requires some electronics assembly, or someone with the skills to do it for you.

Or you could also sell this one (and get ~$1000 perhaps) and use the funds for the brand new one. You'll need to do some pricing and investigation as to which route you want to take.

John


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Losmandy G11G2 on pier; Losmandy G11 with OnStep (rebuild in progress); SkyShed design roll-off observatory; ZWO ASI2600MM-P; ZWO ASI071MC; Sky-Watcher Esprit 100 ED; Celestron C925 Edge HD with 0.7XFR, William Optics Zenithstar 61 APO; PHD2, Sequence Generator Pro and PixInsight user

Good for thought indeed. I got the mount and tripod for $250 donation to an amateur astronomy group that was clearing out some old gear they had so I feel like I have some house money so to speak to play with, plus I feel obligated morally to use it for a few years. I can upgrade in the future for sure.?

I am pretty handy and the simplicity of Losmandy as far as working on them is a big reason I’ve wanted one, I took a quick look at the mount and ordered new clutch pads and bearings and a cleaning kit. When that arrives I will give it a breakdown and clean it thoroughly, lube and see what it feels like. I was able to set it up last night and everything works on the Dig Drive system so that’s great! Do the high precision worm gears help with the very old mounts? I think this may be from the 90’s honestly.?

Bill,

This is my thinking exactly. If the bones are solid I will gladly upgrade other components and be happy for years. I do not own a large refractor so the GM8 will fit handle everything I own nicely.?

Another question is bearing/washer spacer stacking on old mounts. This picture is how they were stacked when I pulled them out, it doesn’t look right to me but I am unsure if this is how they used to do it. Does anyone know if this is right or wrong??

Can't say for sure if that's how they used to do it, but there is typically only one thrust bearing.? Common arrangement is: knob - wavy washer - aluminum spacer - flat washer - thrust bearing - flat washer.? Is there a thrust bearing on the other axis??

Keith

knak,

I will check today and get back. I can’t see how a bearing would ever rest on a wavy washer??

Craig

knak,

this is a picture of the other bearing. Laid out as it was installed. Cap, thin washer, bearing, wavy washer, spacer, bearing and thin washer last closest to barrel bearing? Not sure if exact word for that bearing.?

Hi Craig,

that picture definitely shows a bearing out of place. There should only be one bearing in each axis with the correct order being:
thin washer - bearing - thin washer - spacer - spring washer - knob

I believe Losmandy swaps the order of the spring washer and spacer but, in my mind, the order I suggested provides a more uniform pressure to the bearing (please correct me if I’m wrong).

Maybe that second bearing is the one from the other axis? Someone misplaced it long ago??

Thanks Jonathan,

I agree about the pressure and placement of the bearings and washers. ?It must be wrong if the thrust bearing is seated directly on the spacer instead of being sandwiched between 2 flat thin washers. I have ordered new thin washers, thrust bearings and clutch pads. I dismantled today and cleaned every washer, bearing, spacer and every other surface I could and removed all the old grease. I will replace and lube when parts arrive. I did not remove any worm gears or motors today. If I am upgrading I will let Losmandy do that at the factory. There were actually 2 thrust bearings on the Dec and RA shafts. ?Given this mount was used with the public who knows how, for all I know it could have been used in a "Mount Dismantling" class. I kid but it may have been taken apart and reassembled many times giving an oppurtunity to install bearings/washers improperly. Thanks again for the answers and suggestions!!

Craig

For any other who seek this info this comes form the GM8 manual.

Both R.A. and DEC axes are the same. First, remove the clutch knob. Five parts will come off the shaft. Spring washer, aluminum spacer, thin washer, needle bearing and thin washer.

Hi Craig,

While I know the G11 best, I haven't seen a mount that has two thrust bearings at the bottom end. I'll repeat what others have basically said: knob, black donut, spring washer, flat thrust washer, thrust bearing, flat thrust washer, then the seat inside the mount. I would replace all washers and bearings if you're going this far. The spring washers also lose tension after being compressed for many years. My preferred lube here is the Mobilgrease 28, a high-performance aviation grade lubricant.?

Once you remove the worm and blocks there will be another set of washers and thrust bearings under the ring gear, larger in size. I have replaced these on my mounts in the same fashion and degreased and relubed everything there as well.

Then the ring and worm should be degreased and relubed too. But here the Jet-Lube MP-50 moly grease is used. If you have brass worms, or the stainless worms as well, used caution while handling. Any nick or dent in the gear teeth will cause guiding glitches which you don't want.

If your mount is that old, you may have a different worm than modern day. I think there were some two-piece designs and some with longer quarter inch shafts. You may need the new brass worms to get the Gemini 2 system to fit on. You'll need to check what you have before proceeding.

John

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Losmandy G11G2 on pier; Losmandy G11 with OnStep (rebuild in progress); SkyShed design roll-off observatory; ZWO ASI2600MM-P; ZWO ASI071MC; Sky-Watcher Esprit 100 ED; Celestron C925 Edge HD with 0.7XFR, William Optics Zenithstar 61 APO; PHD2, Sequence Generator Pro and PixInsight user

Hi Craig

Just to reiterate a few other comments

First, the factory order and components are shown in this video here:?



Second, as a few others have pointed out, upgrading a GM8 to the latest release version can be very similar to cost of a new mount. When upgrading a GM8 i'd say the majority opt to sell it and go to a new mount. That's not to say you can't use your mount as is, or with a few upgrades, but generally that's the case. I suggest you give Tanya a ring at the shop and talk to her about this and she can offer some additional insight as well

Brian

John,

Thanks for the reply and the lube recommendations, I will handle with care the parts you mention. I will speak to Tanya or try to about which path to take, after taking a look inside it looks to be in great shape except for the rings, bearing etc. which I have ordered. I will wait to see what I hear from Losmandy before going with big upgrade that would approach the amount of a new mount.?

Craig

Brian,

I meant to say to you that I'll call Tanya and try and speak with her. Any further investment will wait until I speak to them and see what's up. ?The idea of a GM811 is appealing to say the least, I am so fortunate to have this one maybe I'll tune this up a bit and go bigger? ?Another topic for another day to be sure. Thank you all for your help ? ? 1

Craig

Hi Craig,

These extra thrust bearings are probably from someone who had installed encoders but removed them before selling the mount sometime in the past. The new owners did not know any better and just left them on. My advice is to order a set (2 pieces in the kit) of new thick black aluminum spacers to replace these early version small-diameter spacers which appear to have a lot of wear. I also highly recommend new thrust bearings and the matching thrust bearing races (what are referred to as washers but they are actually precision parallel flat ground races) as well as an HP worm for the RA axis. You will want this for imaging even if you keep the #492 Digital Drive for imaging. For modest focal length optics, the Digital Drive works well and can even be guided. The HP worm on the RA axis should improve your unguided and guided imaging results significantly assuring you get it well set up and adjusted. Google Michel Herman and Bellevue spring disc modification for Losmandy mounts.?

I upgraded my old G11 to the latest G11G specs twice and for me, it was worth the cost because it was my trusty old friend. I was also going to do the same for my GM8 Gemini 1 but Covid got in the way and after waiting a year I gave up and ordered a new GM8G and sold my old GM8. The new GM8G is a great mount and I have added 311K encoders and a Nexus DSC for visual use working the mount manually as a PUSH-TO mount which the Losmandy mounts were designed to be used as long before computers and Gemini was available.?For a used mount with little personal history, it may be more cost-effective to buy a new mount if you really want the latest version with all the features like tucked servo motors and sprung OPWs as well as the latest Gemini 2 controller and firmware.?

But if your vintage GM8 is in good shape and not faded it is IME well worth upgrading as they were made as well or better than current production mounts once updated. Plus this mean you can clean it up and enjoy it and upgrade as needed.??

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Chip Louie Chief Daydreamer Imagination Hardware?

? ?Astropheric Weather Forecast - South Pasadena, CA?