Re: Unable to fully lock RA axis on G11
On Sun, Feb 16, 2025 at 10:53 AM, Paul Goelz wrote:
On 2/16/2025 10:47 AM, Chip Louie via groups.io wrote:
The issue of grease migration is caused by using the wrong grease.?
The grease must be able to maintain its viscosity hot or cold to work
but it cannot melt or separate.
Hmmmm..... when I disassembled my GM811 about a year after I bought it
new, I found the clutch area (including the clutch disks) was totally
saturated with grease.? I suspect Losmandy did not use "the wrong
grease".? More likely a side effect of the clutch design. When
assembled, the clutch disk touches the ring gear and bearing. Any grease
in the bearing will slowly flow out onto the clutch disk.? And did.?
Thinking that was a bad thing I cleaned it and re-assembled.? Only to
find the clutches once again covered in grease the next time I
disassembled.
While the clutch was disassembled, I discovered another small issue that
I corrected.? The clutch disk center hole was slightly under sized,
causing the disk to buckle slightly when forced over the shaft.? This
could require excessive clutch tension just to overcome the buckle and
force full clutch engagement.
I continue to wonder why people are so focused on getting a "solid"
clutch lockup.? IT IS NOT NECESSARY.? The only forces I can see that
would cause slippage while tracking would be rotational friction,
imbalance or wind.? Note that rotational friction INCREASES with clutch
pressure (as does erratic tracking) due to the inherent friction in the
cylindrical roller thrust bearings.? I run my clutches very loose.? I
can easily push my scope around even when very cold and it NEVER slips
while tracking.? I have even had a couple sessions where I inadvertently
left the clutches totally loose and it tracked just fine.? I only
discovered it after the fact.? The tighter you run your clutches, the
more you run the risk of introducing other issues like premature thrust
bearing wear and erratic RA tracking.
Paul
--
Paul Goelz
Rochester Hills, MI USA
pgoelz@...
www.pgoelz.com
?
Paul what color was the grease??
?
IME working with telescope mounts for quite some time now the right amount of grease for a well (read this as frequently), maintained mount is just to wet the rollers and/or balls and races with no overflow.? If there is anything more than this too much grease was applied.? It's? pretty simple, if you use the right lubricant and apply it correctly it cannot migrate.??
?
Like I have posted before, I have been using a light touch on the clutches for quite some time for imaging and it works perfectly.? For visual use I run them almost fully free with just the lightest contact so the drive will still track. Of course the payload in the saddle must be well balanced on 3 axes but that is no hardship IME.?
?
IME people that need to have a hard clutch lock up usually have a heavy or long payload that is out of balance and/or contaminated clutches.? This has been my experience other than a few people who had cranked down on the clutches so hard that the clutch plate on the axle was distorted preventing clutches from working due to the much reduced surface area and had to be cut and ground back to flat by Losmandy.? No surprise once flat again the clutches held just fine.??
?
--
Chip Louie Chief Daydreamer Imagination Hardware?
Astrospheric Forecast - South Pasadena, CA?
?
?
?
|
Re: Unable to fully lock RA axis on G11
On Sun, Feb 16, 2025 at 03:19 PM, Paul Goelz wrote:
more to this story
Most likely regarding the clutches.? The topic begins with the characteristics of a Celestron Losmandy G11, something available before they offered the G11 themselves.? Updates and materials, such as to the clutches, have changed over time, and it is uncertain how many service updates occurred.
?
And that which works, suffices for using the mount.? I use a current G11G with SLW in stock configuration, and I engage the clutch using the clutch-knob-set securely (high).? A level at which friction breaks above 10 ft-lbs at the axis, with significant force vectors along the clutch shaft.? With this setting, targets also track within the 0.8 to 0.2 range, depending on the guide star, field, and environmental conditions.? Usually, below 0.5, but in the higher range as wind gets into the 12-knot wind buffet range.
?
Unfortunately, on clutch engagement the available documentation just says: disengaged and engaged.? I am fairly certain from the design there must exist a minimum clutch tension.? One that loads the counterweights on to the lower housing and removes the clutch rod load off the clutch idle pin bearings.? This makes sense as the load carried and the counterweight mass must figure into any minimum level.? And use with the current G11G indicates that just setting the clutches tight also works as expected when tracking.
?
Doug
?
|
Re: Unable to fully lock RA axis on G11
On 2/16/2025 2:00 PM, Thomas Kallenbach via groups.io wrote: Is this the kind of RA tracking that might be caused by clutches being too tight?
It is really hard to say for sure. There are multiple possibilities including atmospheric causes.? But yes, it is possible.? Do the experiment..... loosen your clutches on the same night in the same location in the sky and see if it smooths out.? I typically tighten until I feel contact and then go 1/8 to 1/4 turn more.? Less is more. I spent a great deal of time a year or two ago trying to track down the cause of inconsistent tracking and excessive DEC backlash.? In the process I disassembled and re-assembled, measured, re-greased, tried different greases and made several physical modifications. The end result is that I went from being extremely frustrated with a MINIMUM of 2.5 seconds of DEC backlash to now being extremely happy with the performance.? No RA jumps EVER, and DEC backlash that is consistently between 100 and 800 mS.? Typical tracking is maybe 0.6" RMS on a crummy night and I have seen it as low as 0.3" RMS on a good night. There is more to this story but A) I don't mean to hijack the clutch discussion and B) no one seems to be particularly interested when I bring it up ;) Paul -- Paul Goelz Rochester Hills, MI USA pgoelz@... www.pgoelz.com
|
Re: Unable to fully lock RA axis on G11
Is this the kind of RA tracking that might be caused by clutches being too tight? 
|
Re: Unable to fully lock RA axis on G11
On 2/16/2025 10:47 AM, Chip Louie via groups.io wrote: The issue of grease migration is caused by using the wrong grease.? The grease must be able to maintain its viscosity hot or cold to work but it cannot melt or separate. Hmmmm..... when I disassembled my GM811 about a year after I bought it new, I found the clutch area (including the clutch disks) was totally saturated with grease.? I suspect Losmandy did not use "the wrong grease".? More likely a side effect of the clutch design. When assembled, the clutch disk touches the ring gear and bearing. Any grease in the bearing will slowly flow out onto the clutch disk.? And did.? Thinking that was a bad thing I cleaned it and re-assembled.? Only to find the clutches once again covered in grease the next time I disassembled. While the clutch was disassembled, I discovered another small issue that I corrected.? The clutch disk center hole was slightly under sized, causing the disk to buckle slightly when forced over the shaft.? This could require excessive clutch tension just to overcome the buckle and force full clutch engagement. I continue to wonder why people are so focused on getting a "solid" clutch lockup.? IT IS NOT NECESSARY.? The only forces I can see that would cause slippage while tracking would be rotational friction, imbalance or wind.? Note that rotational friction INCREASES with clutch pressure (as does erratic tracking) due to the inherent friction in the cylindrical roller thrust bearings.? I run my clutches very loose.? I can easily push my scope around even when very cold and it NEVER slips while tracking.? I have even had a couple sessions where I inadvertently left the clutches totally loose and it tracked just fine.? I only discovered it after the fact.? The tighter you run your clutches, the more you run the risk of introducing other issues like premature thrust bearing wear and erratic RA tracking. Paul -- Paul Goelz Rochester Hills, MI USA pgoelz@... www.pgoelz.com
|
Re: G11G Imaging Weight Capacity for Imaging?
On Sat, Feb 15, 2025 at 12:14 PM, Michael Ben-Yehuda wrote:
Welcome to the group Francisco!?
Thanks for the rain! ?
?
Chip,?
This problem for those with large aperture telescopes... gets limited sympathy ??
Just kidding of course.
Thanks for responding as I think the point you make catches many of those with aperture fever by surprise.
There definitely is a wall,? or maybe I should say a glass ceiling, that starts really being felt at around 12" where atmospherics becomes predominant.?
It is a mistake to blame the hardware when it's performance well exceeds the seeing.
Perhaps vendors might not be eager to educate??
?
?
Anyway, I don't want to drift too far off topic, but it is an important consideration when sizing and making hardware choices.
?
?
?
I've owned and observed with different sized optics from 50mm to 355mm as well as different types of telescopes over the years.? As far as what works visually IME the knee in the curve starts with a very good 100mm and maybe just past that bend a good 130mm refractor seems like a realistic visual point of diminishing returns for most folks not living out past Yenterville.? That's Bortle 1 skies for you who don't know it.? For two surface reflector telescopes these same points seem to be about 6" and 8" or so.? ?
?
For a long time I thought the atmosphere so severely limited out ability to observe visually even in a dark sky area.? So why go nuts on the best possible optics good should be good enough.? Okay so I was wrong.??
?
Over time (slow learner), I've discovered the advantage of having really good optics, while only really able to fully deliver under perfect conditions (including using the right high-end back half optics), can ha isve a huge impact on what you can see once you learn to live in between the turbulence.? Those admittedly short moments of clarity can be amazing and if you learn it soon enough almost make the cost worthwhile.??
?
As an imager the advantages of using the best optics is obvious in the data and resulting images.? But for visual observation it is harder to objectively quantify unless you have seen it.? I've seen it and I'm not going back to mediocre optics.??
?
--
Chip Louie Chief Daydreamer Imagination Hardware?
Astrospheric Forecast - South Pasadena, CA?
?
?
?
|
Re: Unable to fully lock RA axis on G11
On Sat, Feb 15, 2025 at 01:40 PM, Michael Ben-Yehuda wrote:
When I first got my (used) G11 it needed to be cleaned and relubricated. It was my first mount in this class of machined hardware and I made my mistakes. The first was not getting the bearings really clean. Who knows what was used before and how old it was, but I ended up with too much lubricant thinking there wasn't enough, and it didn't take long for it to migrate and contaminate the clutch. I knew I'd messed up.?
Do over! .. Got everything really super clean then was super careful about lubricating. Tight tolerances don't need much. I was super careful to separate lubrication from assembly, not touching anything else when lubricating bearings and wearing gloves to be sure.
Might have been overkill, but it worked.
?
This mount is different than what I was used to and it took some time for me to adjust.?
?
Nice to have the option for the enhanced friction pads?
?
Clear skies,?
?
Michael?
?
?
?
That's the trick isn't it, most people think more grease is good and they are correct up to the point when it is too much.? ?The surprise for most people is that just enough comes a lot sooner than they realize.??
?
The real trick though is to use a lubricant with the correct characteristics for the application.? Most greases will tend to separate over time.? There are only a few reasons the clutches get contaminated which is the most common reason for slippage.?
?
The most common issue is the clutch surfaces have been contaminated with oil and/or were not really clean when reassambled. The oils from grease tend to stay on/in the plastic disc unless a strong solvent is used.? The clutch surfaces must be clean and dry when the mount is assembled or slippage is going to happen. If in doubt just replace the plastic disc with a new one, they are inexpensive.? Just be sure to clean both outer mount clutch plates before you install the new disc or you will have the same issue.?
?
The issue of grease migration is caused by using the wrong grease.? The grease must be able to maintain its viscosity hot or cold to work but it cannot melt or separate.? Common automotive greases tend to separate when sitting there doing nothing and when warmed that separation speeds up. These greases also tend to stiffen when cold which adds resistance to movement.? The hot grease separated oil is usually what migrates and causes a slipping clutch problem.?
?
I have been using a pure synthetic oil based grease called Superlube with Teflon for decades.? It has a wide temperature range and doesn't separate when hot, outstanding standards tested wear and pressure characteristics and maintains very low start up torque when cold.? I have been experimenting with adding microscopic sized Molybdenum to Superlube lube for a year but have not seen any advantage to doing so.? It does make a black mess and makes it impossible to see when the normally milky white Superlube is contaminated and in need of cleaning and relubrication.?
?
That said the recommended Losmandy grease kit is also an excellent choice for those who want a known to work lubricant package.?
?
--
Chip Louie Chief Daydreamer Imagination Hardware?
Astrospheric Forecast - South Pasadena, CA?
?
?
?
|
Re: Unable to fully lock RA axis on G11
When I first got my (used) G11 it needed to be cleaned and relubricated. It was my first mount in this class of machined hardware and I made my mistakes. The first was not getting the bearings really clean. Who knows what was used before and how old it was, but I ended up with too much lubricant thinking there wasn't enough, and it didn't take long for it to migrate and contaminate the clutch. I knew I'd messed up.?
Do over! .. Got everything really super clean then was super careful about lubricating. Tight tolerances don't need much. I was super careful to separate lubrication from assembly, not touching anything else when lubricating bearings and wearing gloves to be sure.
Might have been overkill, but it worked.
?
This mount is different than what I was used to and it took some time for me to adjust.?
?
Nice to have the option for the enhanced friction pads?
?
Clear skies,?
?
Michael?
?
?
?
?
|
Re: G11G Imaging Weight Capacity for Imaging?
Welcome to the group Francisco!?
Thanks for the rain! ?
?
Chip,?
This problem for those with large aperture telescopes... gets limited sympathy ??
Just kidding of course.
Thanks for responding as I think the point you make catches many of those with aperture fever by surprise.
There definitely is a wall,? or maybe I should say a glass ceiling, that starts really being felt at around 12" where atmospherics becomes predominant.?
It is a mistake to blame the hardware when it's performance well exceeds the seeing.
Perhaps vendors might not be eager to educate??
?
?
Anyway, I don't want to drift too far off topic, but it is an important consideration when sizing and making hardware choices.
?
?
|
Re: G11G Imaging Weight Capacity for Imaging?
I sold my G11G w/ LW Tripod to Francisco.? Please welcome him and help him out when he has questions.
------------------------
Jim W
Phoenix, AZ. USA
Losmandy G11G w/ L6, NINA 3.0 / ASTAP, ASI2600MC Pro, Sky-Watcher Scopes, Canon L Lenses.
|
Re: Unable to fully lock RA axis on G11
On Thu, Feb 13, 2025 at 06:55 PM, <avishekaiyar@...> wrote:
I am going to try a few imaging sessions to see if there is a real problem.?
?
Then my next step would be a regressing if needed.?
?
Thanks for the tip on the high friction clutch pads. Will surely keep that in mind.?
?
Many thanks.
?
Avi?
?Avi,
?
It really is dependent on having a well balanced payload in the saddle.? Check out this guy's method of balancing.? This is basically what I have been doing for every mount and scope I have owned for the last 50 years.??
?
?
Hope this helps.?
?
--
Chip Louie Chief Daydreamer Imagination Hardware?
Astrospheric Forecast - South Pasadena, CA?
?
?
?
|
Re: Unable to fully lock RA axis on G11
I am going to try a few imaging sessions to see if there is a real problem.?
?
Then my next step would be a regressing if needed.?
?
Thanks for the tip on the high friction clutch pads. Will surely keep that in mind.?
?
Many thanks.
?
Avi?
|
Re: G11G Imaging Weight Capacity for Imaging?
On Tue, Feb 11, 2025 at 07:08 PM, joe kuhl wrote:
Hello Francisco,
?
<< SNIPPED >>
?
Image scale is what you need to track under.? Your periodic error has to be less than your image scale you are shooting at.? With a 2600 camera that has 3.76 micron pixels, you need to guide under .4, that is a 12 LX200 OTA with a .63 reducer.? With a 2400 camera you are at .64, more manageable but still kind of tough to do.? My opinion.? Reason,? you have a 14" barrel that is over 24" long with a dew shield on top of that mount. A 6" RA and Dec gears driving it. ?
?
<< SNIPPED >>
?
Joe
?
I don't understand how you came up with this.? Regardless of optical resolution or camera seconds per pixel image scale or how well the mount tracks the rate limiting factor when imaging from the surface of the Earth is the quality of the air column between the sensor and the object.??
?
--
Chip Louie Chief Daydreamer Imagination Hardware?
Astrospheric Forecast - South Pasadena, CA?
?
?
?
|
Re: Unable to fully lock RA axis on G11
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
?
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.?
?
--
Chip Louie Chief Daydreamer Imagination Hardware?
Astrospheric Forecast - South Pasadena, CA?
?
?
?
|
Re: Unable to fully lock RA axis on G11
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
|
Re: Unable to fully lock RA axis on G11
?
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.? ? ??
?
--
Chip Louie Chief Daydreamer Imagination Hardware?
Astrospheric Forecast - South Pasadena, CA?
?
?
?
|
Re: G11G Imaging Weight Capacity for Imaging?
Joe
?
Same question as Chip.? Walk us through the math.? Yes, an AP mount or above would be better.
------------------------
Jim W
Phoenix, AZ. USA
Losmandy G11G w/ L6, NINA 3.0 / ASTAP, ASI2600MC Pro, Sky-Watcher Scopes, Canon L Lenses.
|
Re: G11G Imaging Weight Capacity for Imaging?
On Tue, Feb 11, 2025 at 07:08 PM, joe kuhl wrote:
Hello Francisco,
?
<<SNIPPED>>
?
Image scale is what you need to track under.? Your periodic error has to be less than your image scale you are shooting at.? With a 2600 camera that has 3.76 micron pixels, you need to guide under .4, that is a 12 LX200 OTA with a .63 reducer.? With a 2400 camera you are at .64, more manageable but still kind of tough to do.? My opinion.? Reason,? you have a 14" barrel that is over 24" long with a dew shield on top of that mount. A 6" RA and Dec gears driving it. ?
?
<<SNIPPED>>
Joe
?
I'd like to hear how you calculated these numbers.? What is the method and why?? ? ?
?
--
Chip Louie Chief Daydreamer Imagination Hardware?
Astrospheric Forecast - South Pasadena, CA?
?
?
?
|
Re: G11G Imaging Weight Capacity for Imaging?
Yeah Joe, a set screw.??
As you say, there are bigger mounts to be had and at bigger price points.
Tracking/Guiding is a discussion all of its own!.
If DSO at native FL were the primary purpose I might think differently, but IMO there's a long way to go before the mount would become the limiting factor.
?
Michael?
|
Re: G11G Imaging Weight Capacity for Imaging?
What is a grub screw??? Is it like a set screw??
?
Joe
|
Chip Louie
Ron