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Hello All?
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I am a brand new user of Losmandy mounts. My past experience with GEMs has been limited to the iOptron SGP and the Vixen GPDX.?
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I recently acquired a Celestron Losmandy G11.?
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I tried to counterbalance my setup today and had a clarification about the RA axis.?
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No matter how much I tighten the RA clutch knob I am unable to fully lock the RA axis movement (and I really tightened the clutch). The Dec axis is fine....I am able to fully lock down that axis when I tighten the Dec clutch.?
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Is this normal ? As an example when I deliberately throw the RA axis off balance by moving the 11lb counterweight all the way towards the end of the shaft, the mount easily rotates about the RA axis even when fully tightened down.?
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This has definitely not been my experience on the other gems I have used...
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Would appreciate any advice.?
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Sincerely?
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Avi?
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Avi,
It is difficult to judge without seeing what you are doing.
You should always be reasonably balanced, the clutches are not designed to hold an unbalanced setup.
You should not tighten the clutches more than necessary, they are designed to be tightened by hand and should hold the telescope but if you knock it they may slip.
The clutches do not lock the mount axes, they hold them.
If you are easily able to move either axis it may indicate that grease has made its way onto the clutch plate(s), which would require a partial strip down and clean.
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On 8 Feb 2025, at 3:41?pm, avishekaiyar via groups.io <avishekaiyar@...> wrote:
Hello All?
?
I am a brand new user of Losmandy mounts. My past experience with GEMs has been limited to the iOptron SGP and the Vixen GPDX.?
?
I recently acquired a Celestron Losmandy G11.?
?
I tried to counterbalance my setup today and had a clarification about the RA axis.?
?
No matter how much I tighten the RA clutch knob I am unable to fully lock the RA axis movement (and I really tightened the clutch). The Dec axis is fine....I am able to fully lock down that axis when I tighten the Dec clutch.?
?
Is this normal ? As an example when I deliberately throw the RA axis off balance by moving the 11lb counterweight all the way towards the end of the shaft, the mount easily rotates about the RA axis even when fully tightened down.?
?
This has definitely not been my experience on the other gems I have used...
?
Would appreciate any advice.?
?
Sincerely?
?
Avi?
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Hi Paul
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This is super valuable. I will try to take a video tomorrow and share it but based on what you are saying I think the mount is functioning normally.?
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The clutches do hold the telescope. But as you said, if the load isn't properly balanced, it no long holds it in place.?
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But I definitely feel that that Dec axis "holds" better than RA.?
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Many thanks.
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Avi?
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On 2/7/2025 11:41 PM, avishekaiyar via groups.io wrote: No matter how much I tighten the RA clutch knob I am unable to fully lock the RA axis movement (and I really tightened the clutch). The Dec axis is fine....I am able to fully lock down that axis when I tighten the Dec clutch. The clutches are just that.... friction clutches.? If any grease has made it onto the friction surfaces (and it will) they cannot be "locked".? NOR SHOULD THEY.? The more you tighten the clutches the more load you put on the thrust bearings.? The thrust bearings use cylindrical rollers that roll in a circle.? And if you think about the geometry of a cylinder rolling in a circle, it will be obvious that it CAN'T unless one end or the other slips.? And if they slip unevenly, you can get RA jumps.? So the tighter the clutches, the more drag and unevenness from the rollers. Once I realized this I tried running with very loose clutches and all my RA jumping went away.? I don't know if it made a difference but I also cleaned the thrust bearings and re-greased with MP-50 since in essence, the rollers are a high pressure sliding interface.? I normally tighten until I feel contact and then go a maximum of 1/8 to 1/4 turn farther.? But, I can even run with the RA clutch fully loosened..... the rig is well balanced (that is key) and simply the weight of the rest of the mount and load is sufficient to provide enough friction. My $0.02 anyway. Paul (another one) -- Paul Goelz Rochester Hills, MI USA pgoelz@... www.pgoelz.com
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Avi,
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Chances are your clutch discs are very oil and/or severely worn. You will need to unscrew the clutch locks all the way off and pull the shaft up and out of the mount to inspect. Remember the order of the knob, washers are bearings and put back in the same order. Try wiping down the disc pad with alcohol or some other solvent. If the discs are worn like a phonograph record, they may need to be replaced. You can give them some extra life by doing a light sanding and again wiping clean. You will need to clean the respective upper and lower contact surfaces as well. But I would suggest ordering new ones from Lomandy if they are really worn. This should give you some extra stiction and allow the locks to grip down on something less slippery.
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John
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Losmandy G11G2 on pier; refurbed Losmandy G11 with OnStep controller; SkyShed design roll-off observatory; ZWO ASI2600MM-P; ZWO ASI071MC; Sky-Watcher Esprit 100 ED with field flattener; Celestron C925 Edge HD with 0.7XFR, William Optics Zenithstar 61 APO; PHD2, NINA, Sequence Generator Pro and PixInsight user
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Hi John?
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I will take a look right now and report back.
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Thanks.
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Avi?
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It’s
not supposed to “fully” lock!.. I have Michael Herman’s high friction clutch
discs and a perfectly working G11 and with enough force, it’ll move..
It
doesn’t take much force on the knobs to sufficiently tighten the clutches..
Derek
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From: [email protected] [mailto:[email protected]] On Behalf Of John Kmetz via groups.io
Sent: Saturday, February 08, 2025
7:50 AM
To: [email protected]
Subject: Re: [Losmandy_users_io]
Unable to fully lock RA axis on G11
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Chances are your clutch discs are very oil and/or severely worn. You
will need to unscrew the clutch locks all the way off and pull the shaft up and
out of the mount to inspect. Remember the order of the knob, washers are
bearings and put back in the same order. Try wiping down the disc pad with
alcohol or some other solvent. If the discs are worn like a phonograph record,
they may need to be replaced. You can give them some extra life by doing a
light sanding and again wiping clean. You will need to clean the respective
upper and lower contact surfaces as well. But I would suggest ordering new ones
from Lomandy if they are really worn. This should give you some extra stiction
and allow the locks to grip down on something less slippery.
_____________________________________________________________________________________________________________________________________________________________________________
Losmandy G11G2 on pier; refurbed Losmandy G11 with OnStep controller; SkyShed
design roll-off observatory; ZWO ASI2600MM-P; ZWO ASI071MC; Sky-Watcher Esprit
100 ED with field flattener; Celestron C925 Edge HD with 0.7XFR, William Optics
Zenithstar 61 APO; PHD2, NINA, Sequence Generator Pro and PixInsight user
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Dear John?
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I just separated the RA and Dec axes and disassemble the RA assembly (remove spacer, wavy washer, 3 piece thrust bearing and finally the RA shaft).?
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Everything checks out. The clutch pad looks in a really good condition too.?
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If I had to really nit pick, I would say that the wavy washer has lost a lot of its waviness. :)?
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But after reading some of the other comments, I sort of see the point. With the Dec axis removed, the RA movements are pretty "locked" when the RA clutch is tightened (I made sure not to over tighten....I tightened it and let go as soon as I felt some resistance ). So I think it's ok.?
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I also saw in one of the Losmandy balancing videos, Brian Valente also mentioning that the Dec axis is a lot "freer" compared to RA..I felt the exact same way so I guess it's all design intent.?
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Thanks.
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Avi?
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Hi Derek,?
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That makes sense.?
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Thanks for pointing that out?
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Avi?
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On Sun, Feb 9, 2025 at 12:24 AM, <avishekaiyar@...> wrote:
I just separated the RA and Dec axes and disassemble the RA assembly (remove spacer, wavy washer, 3 piece thrust bearing and finally the RA shaft).?
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Everything checks out. The clutch pad looks in a really good condition too.?
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If I had to really nit pick, I would say that the wavy washer has lost a lot of its waviness. :)?
?
But after reading some of the other comments, I sort of see the point. With the Dec axis removed, the RA movements are pretty "locked" when the RA clutch is tightened (I made sure not to over tighten....I tightened it and let go as soon as I felt some resistance ). So I think it's ok.?
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I also saw in one of the Losmandy balancing videos, Brian Valente also mentioning that the Dec axis is a lot "freer" compared to RA..I felt the exact same way so I guess it's all design intent.?
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Hi Avi,
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The locks never absolutely grip things down without movement. There is still a little play if you turn them hard enough. So the scope will move a bit if you bump into it or if it is very unbalanced or starts to drag a cable. I gave up on the wavy washer and balance RA by cranking ALT down to 0 (but careful you don't tip over if trying that). You could try new discs anyway or try the Michael Herman high friction discs, as Derek mentioned). Getting enough stiction for a night's operation should not be a hard thing.
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Good luck.
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John
--
_____________________________________________________________________________________________________________________________________________________________________________
Losmandy G11G2 on pier; refurbed Losmandy G11 with OnStep controller; SkyShed design roll-off observatory; ZWO ASI2600MM-P; ZWO ASI071MC; Sky-Watcher Esprit 100 ED with field flattener; Celestron C925 Edge HD with 0.7XFR, William Optics Zenithstar 61 APO; PHD2, NINA, Sequence Generator Pro and PixInsight user
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On Fri, Feb 7, 2025 at 08:41 PM, <avishekaiyar@...> wrote:
Hello All?
?
I am a brand new user of Losmandy mounts. My past experience with GEMs has been limited to the iOptron SGP and the Vixen GPDX.?
?
I recently acquired a Celestron Losmandy G11.?
?
I tried to counterbalance my setup today and had a clarification about the RA axis.?
?
No matter how much I tighten the RA clutch knob I am unable to fully lock the RA axis movement (and I really tightened the clutch). The Dec axis is fine....I am able to fully lock down that axis when I tighten the Dec clutch.?
?
Is this normal ? As an example when I deliberately throw the RA axis off balance by moving the 11lb counterweight all the way towards the end of the shaft, the mount easily rotates about the RA axis even when fully tightened down.?
?
This has definitely not been my experience on the other gems I have used...
?
Would appreciate any advice.?
?
Sincerely?
?
Avi?
?
Do you recall the scene in Star Wars when Luke is introduced the his father's lightsaber?? The core of the Losmandy mount design is a lot like that lightsaber.? The G11 and GM8 were designed in a more civilized age, from a more elegant time.??
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When the G11 was designed we used to be able to see the sky and learned how to navigate it.? Everyone learned the night sky and used the Thomas Bros. Map book of the sky called Sky Atlas 2000.? There were no GOTO "blasters" there was only personal knowledge and the skill needed to PUSH-TO your chosen object.? The original Losmandy Digital Drive simply moved the RA axis in sync with the local system and galaxy and you pushed the scope to your destination.?
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To do this you needed a well designed, finely tuned machine and the mount needed to be well balanced with the scope in the saddle.? We ran the clutches fully or almost fully open / loose and used a finger or two to push the telescope tube to the desire object using personal knowledge and skill.? There was no need to lock the axis, this was simply unnecessary.?
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With the advent or the Gemini and GOTO becoming the more widely used method of observation people with less skill could navigate the night sky once the learned some simple skills to align the mount with the night sky.? The advent of the GOTO computer brought many new observers to the hobby and the lack of knowledge caused a lot of frustration among the novices.? Those who couldn't or wouldn't adapt and invest the the time to learn these small skills usually left the hobby.??
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There is no reason to cinch down the clutches on a Losmandy mount for GOTO or imaging use, none.? The only catch is the mount has to be in good mechanical condition (well adjusted, clean and lubed), the payload balanced in the saddle on 3 axis and you can not have any cable snags.? If your Losmandy mount meets these simple conditions it will guide very well, easily sub 0.5" error with only modestly snugged clutches.??
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--
Chip Louie Chief Daydreamer Imagination Hardware?
Astrospheric Forecast - South Pasadena, CA?
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This may be one of the messages we really need to get out -- that the clutches are not meant to be fully tightened, and what you should do is see how little tightening is sufficient to keep them from slipping with your setup.? For me, it is about 1/4 turn past the point where resistance is first felt.
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I wonder if this could be what is causing my jerky RA guiding.? Thinking that loose clutches might be the problem, I tightened them down pretty tight.
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Michael H's friction disks are made from what looks to me to be high temp automotive gasket material. They are very similar to the system used by Celestron on the Nexstar one armed mounts. These again are not designed for rigid mount of the saddle and should have limited slippage to protect the drive train components.
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On Mon, Feb 10, 2025 at 11:13 AM, George Cushing wrote:
Michael H's friction disks are made from what looks to me to be high temp automotive gasket material. They are very similar to the system used by Celestron on the Nexstar one armed mounts. These again are not designed for rigid mount of the saddle and should have limited slippage to protect the drive train components.
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I was an early proponent of Michael Herman's high friction clutch discs and I use my Losmandy G11G and GM8G mounts for both imaging and visual. But if you are a dedicated imager and will never use the mount in PUSH-TO mode as it was designed to be used they are great.? I used the high friction discs for a year and a half and they never really broke-in.? They have a much higher friction level than the stock Losmandy plastic clutch discs and they do not like to be used in the slip mode, they are grabby and in the cold they can be noisy making a creaking sound when being asked to slip.? So when Scott rebuilt my G11s to the latest G11G specs he tossed them and installed new discs which restored the great PUSH-TO freedom I prefer.? ?
? ? ? ??
--
Chip Louie Chief Daydreamer Imagination Hardware?
Astrospheric Forecast - South Pasadena, CA?
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Once I changed to the Michael Herman high friction discs I never went back. They really prevent slippage and don't come loose like the plastic ones, so you don't have to keep cranking down for them to stay put. However, they are so grippy you cannot really do a balance in RA while the mount is at the typical altitude for one's latitude needed for proper PA. But my mount is on a pier, and I can crank the altitude down to near zero so there is little downward force on the clutch assembly, and I can rock it back and forth freely to balance. If you are using a tripod, the zero-ALT position is harder to reach without tipping over or adding some hanging weights under the tripod. Still, these discs are one option for better RA stability. If RA lock is still hard to achieve, this sounds like some washer, disc or bearing in the whole assembly might be worn down to the point where a typical knob twist does not stop RA movement as there is too little contact between the mating surfaces. But the only way to check this would be to take the RA drive apart and put a micrometer on each of the parts to see if something is too thin (and with a bit of time invested).?
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John
--
_____________________________________________________________________________________________________________________________________________________________________________
Losmandy G11G2 on pier; refurbed Losmandy G11 with OnStep controller; SkyShed design roll-off observatory; ZWO ASI2600MM-P; ZWO ASI071MC; Sky-Watcher Esprit 100 ED with field flattener; Celestron C925 Edge HD with 0.7XFR, William Optics Zenithstar 61 APO; PHD2, NINA, Sequence Generator Pro and PixInsight user
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As designed the Losmandy mounts work well if the mount is in good mechanical condition with clean dry clutch discs and a well balanced payload.? It's pretty simple, if you need to crank down on the clutches to avoid slippage there is something wrong with your mount or how it is being used.? ? ??
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--
Chip Louie Chief Daydreamer Imagination Hardware?
Astrospheric Forecast - South Pasadena, CA?
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Avi
A Long long time ago I had the same problem. I’m using 53 pounds of counterweight and with my attached 80 mm piggyback to my 10 inch RC at certain positions in the sky I would get slippage with the stock nylon Losmandy clutches even though I hand tightened the knobs as tight as I could . Michael Herman’s disc clutch was a game changer for me. I am an imager and keep the knobs tight, I platesolve then move the mount through gemini.net - not into the visual push to technique?
most likely this will solve your problem and then you will have more fun
Ron
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On Wed, Feb 12, 2025 at 09:28 PM, Ron wrote:
Avi
A Long long time ago I had the same problem. I’m using 53 pounds of counterweight and with my attached 80 mm piggyback to my 10 inch RC at certain positions in the sky I would get slippage with the stock nylon Losmandy clutches even though I hand tightened the knobs as tight as I could . Michael Herman’s disc clutch was a game changer for me. I am an imager and keep the knobs tight, I platesolve then move the mount through gemini.net - not into the visual push to technique?
most likely this will solve your problem and then you will have more fun
Ron
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The amount of counterweight should not make a difference.? The most counterweight I have used was:? 3x21 + 1x11 + 1x7 = 81 pounds total CW.? But even my typical 70 pounds of CW shows no slippage while imaging. The clutches are firm to be sure but still only hand tight.? Just don't bump anything and you'll be fine.?
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--
Chip Louie Chief Daydreamer Imagination Hardware?
Astrospheric Forecast - South Pasadena, CA?
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I am going to try a few imaging sessions to see if there is a real problem.?
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Then my next step would be a regressing if needed.?
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Thanks for the tip on the high friction clutch pads. Will surely keep that in mind.?
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Many thanks.
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Avi?
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Chip Louie
Ron