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On Sun, Dec 31, 2023 at 06:01 AM, @VictoryPete wrote:

What is your primary mount?

Sky-Watcher CQ350.? The G11G is my portable mount.? The CQ350 is setup at my cabin in northern AZ.? I wanted a Mach2 but decided the price was too high.

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Jim W
Phoenix, AZ. USA

Losmandy G11G w/ L6, NINA 3.0 / ASTAP, ASI2600MC Pro, ASI533MM Pro,?Sky-Watcher Scopes, Canon L Lenses.

Since the conversation has drifted to belt drives in RA, despite the title, I've changed the title.? Let me share what I learned with a mount of another brand.

Microstepped stepper motors do not have equal torque at all microsteps.? As a result, they tend to have a small cyclical error over the period of a full set of microsteps, on the order of a second (too short for PHD2 to pick up). (They get behind during the part of the cycle where the torque is lower, then catch up.)? I was able to see this in planetary videos, and of course it puts a lower limit on your guiding accuracy in deep-sky work.

Better circuit design reduces the problem but does not eliminate it.

That is why I chose a servo-motor Losmandy for my current mount. I haven't upgraded to Gemini Level 6 but am hopeful that it will become even smoother.

Belt drives like everything else have their own issues.?

LOL, so the mount is also bad at selling itself? LOL.

Try offering your "bad" mounts at market prices, not what you imagine you think they are worth during a season when people are likely to buy it. Pull down your for sale posts and put them back up in the spring at a reasonable price and they will sell.?

It doesn't help that you both have posted and complained about how bad your mounts are. Additionally posting they don't work how you think they should work and how you can't figure out how to use them unlike about 99.9% of other Losmandy owners.?

It is strange that you guys just keep on being the victims here, I think you seem to enjoy it.?

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Chip Louie Chief Daydreamer Imagination Hardware?

? ?Astrospheric Weather Forecast - South Pasadena, CA?

On Sat, Dec 30, 2023 at 11:51 PM, Jim Waters wrote:

I gave up trying to sell my G11G.? Its my secondary mount now.

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Jim W
Phoenix, AZ. USA

What is your primary mount?

I gave up trying to sell my G11G.? Its my secondary mount now.

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Jim W
Phoenix, AZ. USA

Losmandy G11G w/ L6, NINA 3.0 / ASTAP, ASI2600MC Pro, ASI533MM Pro,?Sky-Watcher Scopes, Canon L Lenses.

Since I now have an EQ8-R Pro and the stubborn G11 that doesn't want to sell, and they both easily install on my Primalucelab C120 pier, it is interesting to compare and contrast them. The EQ8R-Pro is super quiet and smooth with the belt driven stepper motor, whereas the G11 is noisy and doesn't seem so smooth. I think the pro and cons with both of these is tied at this point, they just are different for each mount.

On Fri, Dec 29, 2023 at 12:15 PM, @VictoryPete wrote:

What make and model mount is that? Direct drive seems like a good idea.

Pete,

Direct drive using stepper motors are not a great idea. Do the math and watch what happens to your drive line smoothness and controller granularity when you switch to a micro stepping motor while tracking.

The Losmandy GM8 & G11 mounts use a reduction gearbox for a reason. Smoother and finer mount motion.detection and control.

The recent L6 firmware updates had a massive amount of time invested beyond merely updating and bug killing for use with modern imaging applications. The bulk of the time was spent on L6 development to increase control detection granularity and movement to improve tracking smoothness. Once the servo motor PIC chip code was completely rewritten to operate using quadrature detection correctly additional issues required fine tuning the control software to eliminate issues that were not present when not using the very high resolution position data now available to the Gemini 2.?

The amazing thing is it worked and most mounts in good condition and using PHD2 see improved guiding and tracking.?

BTW that is the classic Losmamdy 2-piece worm drive on a G11.?

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Chip Louie Chief Daydreamer Imagination Hardware?

? ?Astrospheric Weather Forecast - South Pasadena, CA?

Hi Chip,?
Ok the DEC motor is as quiet as my belt driven eq6-r pro now, thanks for the tip NOT overtighten it!
RA is better, but not as quiet as DEC but, I'll leave it for now think maybe that's just the way it is, plus, those AC units outside in the neighbourhood overpower this RA motor easily :-P

Yue

What make and model mount is that? Direct drive seems like a good idea.

Thanks Chip, I'll give it a try!

George, I don't have an explanation for that either, but the method from that 2nd video did help eliminating the backlash - that is, leave a little space, torque the gear and press the block in the direction as shown in that video, tight the cover, then adjust the spring screw.
Adjust only the spring screw (like in the first video) resulted either no backlash but extremely tight spur gear, or smooth spur gear but also backlash.
P.S. George, actually, I think this is what happened in my case, quote Chip's post: "The most common reported issue is worm bearing block shift."

Yue

That spacing isn't relevant.

?The end play of the worm is controlled by the positioning of the bearing blocks.?

I don't see how you can avoid backlash with the all the gears in the motor's reduction unit and the two that transfer power from the reduction unit to the worm. That's the benefit a a direct coupling to the motor's output.

Yue,

If the mount is loud when slewing you might improve the whining sound by adjusting the servo motor pinion to gear box mesh.

This is accomplished by loosening the two servo motor mounting screws just enough to allow a small amount adjustment reducing the depth of the servo motor pinion mesh. Feel free to move the servo mesh until it is as quiet as possible. The trick is to NOT over tighten the mounting fasteners, use just enough torque to hold, no more.

This little tip also helps minimize the whining noise and prevents gearbox thread damage and distortion of the gear boxes.?

Cheers!


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Chip Louie Chief Daydreamer Imagination Hardware?

? ?Astrospheric Weather Forecast - South Pasadena, CA?

Truth be told,? Opted for the 151PHQ.?? Smaller, less focal length, better image scale for the cameras I have, a little more forgiving on the tracking / guiding too.? Not to mention easier going through the gate in the backyard.

Thank you everyone,?? Joe

Ok John, I'll go read more on this 76s error, I think now I got the basic, general idea what it is and I'll keep an eye on it.
Yes, the DEC backlash was the only issue I've had, RA was fine straight after assembling, nothing adjusted.
Compares to my other mounts this one is loud while slewing LOL

Yue

On Thu, Dec 28, 2023 at 11:08 PM, @darkairmouse wrote:

BTW, I completely understand and can see the point as some of you suggested just try imaging first and others suggested to adjust it like right away, both are good information and advice.?
Besides adjusting myself to get used to this new mount, there also are a lot of things I need to learn such as the the "76s"?John mentioned. I've never heard that term before, and still not sure if I understand it after readings..?

Hi Yue,

If you search for 76s error in this forum, I think you will many past conversations on the topic. If the worm bearings are not axially compressed, the balls will not ride in the inner race grooves perfectly, and you can see a large PE at that frequency. Since it is not a multiple of the worm period, a PEC curve will not remove it. Holding the bearings inwards while tightening will aid this a bit. Many of us have done a Bellville spring washer mod that involved have the bearing away from the spur gears float inside the block and let the spring tension compress it. Or there are other mechanical mods you can do which involves tearing the mount apart. Such modifications will void your Losmandy warrantee, so think about those later.?

If you now have a backlash adjustment you like, try a guiding run with PHD2 and see what you have achieved. You can check your PHD2 guide log, usually found in your Documents folder and then analyze with PHD2 Log Viewer or PEMPro Log Viewer to see where you stand. There are some HC adjustments you can make to Dec guiding if you are seeing a bit too much backlash there. It sounds like you were not too concerned with RA, so hopefully that is already adjusted well.

CS,

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, Sequence Generator Pro and PixInsight user

Thank you Chip!
Yes I'm moving to Losmandy to continue imaging - came from Skywatcher type mounts, an Orion Sirius and an EQ6-R Pro. I've tuned both of them myself and got used to reduce backlash as much as I can...
I knew there would be some kind of 'culture shock' once I jumped to Losmandy, and was going to leave it along for now till I put it under the stars, but,?that amount of backlash really bothered me as I would never go with that if that's one of my Skywatchers It almost feels like the saddle is loose.... :-) I know no one would try to move their scope by hand while imaging but I was like, what if I have a heavier scope like a GSO 10" CC?? (side track: I think my local sky condition limits the max aperture and focal length as no more than 10" and ~3000mm-ish). One of the reasons I picked this 811G is in case one day I decide to get that GSO 10" CC - or some crazier stuff.
So, just like Paul later said, I too decided to take the matters into my own hands and went on making adjustments because, I agree and understand that this kind of things I'll do eventually- the problem I've had didn't seem to be the one showing in the first SLW adjustment video. I believe mine is exactly the same issue you mentioned as "The most common reported issue is worm bearing block shift.", because the 2nd SLW adjustment video did help.
BTW, I completely understand and can see the point as some of you suggested just try imaging first and others suggested to adjust it like right away, both are good information and advice.?
Besides adjusting myself to get used to this new mount, there also are a lot of things I need to learn such as the the "76s"?John mentioned. I've never heard that term before, and still not sure if I understand it after readings..?

Now the Gemini 2, I've connected it to my MeLE Quieter3Q via direct ethernet, made the basic configurations (site, time, etc.) installed ASCOM drive and have no issue to use it in Astroart - I've been using Astroart some years now, but still I use PHD2 for guiding.??
So it seems I'm all set for imaging, just waiting for the next clear night (likely next year), and I sure will share my experience here!
Thanks again, guys!

Yue

On Wed, Dec 27, 2023 at 11:48 AM, <darkairmouse@...> wrote:

Hi there,
New to Losmandy - just received my first one today, an 811G and just doing some indoor tests after I assembled it.
I've noticed there seems to be quite a bit backlash in the DEC. I did tighten the clutch but still I can move the DEC by turning the counterweight shaft, and can even hear a sound when it moves, sounds like it is bouncing between gear teeth...
I understand this particular 'issue' has been reported probably too many times but still I'm a bit concerned - is this backlash normal, or I need to do some adjustments myself?


Thanks a bunch!
Yue

Hi Yue,?

Welcome to the Losmandy club! Are you currently imaging and moving to Losmandy to continue imaging or are you a visual user??A lot of new Losmandy owners get all up on the tire about what appears to be backlash as new Losmandy owners. What most of us learn over time is what does it matter if something feels out of place but the results work well.

Some of the backlash is due to the way the spring loaded one-piece worm mounts are implemented. It is the nature of the beast to exhibit some springiness on the axles when exerting external force on them. But AFAIK nobody pushes on their counterweight or scope tube while imaging and the observed springiness has little impact on measured guiding results.?

That said the Losmandy drive system has some parts that tend to loosen and yours may have done so in shipping. The most common reported issue is worm bearing block shift. When this occurs the additional space allows some axial play between the worm shoulder and bearings. This is commonly reported as feeling like flipping from one worm face to the other when in fact it is the gap between the worm shoulder and bearing. The other commonly seen issue in this area is the small grub screws on the Oldham coupler loosen just enough to allow some rotational movement and this often manifests as backlash lag with a long period. Unfortunately both of these issues present in the same way and the only solution once you have checked the spring and worm lift are correctly set is partial disassembly to retorque the Oldham coupler grub screws (2 per coupler) and squeeze and torque the worm bearing block fasteners to minimize axial play.?

But being both a new mount and a new user my suggestion is to set up your new mount and use it and learn how the Gemini 2 works and if imaging get you guide scope and camera setup and optimize the autoguiding software and then measure the unguided PE and guided PE error to see if you need to even touch the drive system or not. Then let us know how it works.?
?
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Chip Louie Chief Daydreamer Imagination Hardware?

? ?Astrospheric Weather Forecast - South Pasadena, CA?

On Thu, Dec 28, 2023 at 11:41 AM, HenkSB wrote:

that transporting a mount with the clutches tight (which he did) can cause that too.

Didn't know that, and I'm sure I would do the same if you haven't mentioned it!?

My own G11S had way more backlash than I liked.? One participant at the Kaibab Star party with a G11 that just had an RA extension installed that came fresh from Losmandy claimed that it was delivered with a large amount of backlash.? I'm not sure if it was caused by Losmandy because he was unaware that transporting a mount with the clutches tight (which he did) can cause that too.? I would not trust the backlash to remain unchanged during delivery transportation.? Unless you pick it up yourself, like I did.? At any rate, just learn to make the adjustments ASAP, which you will have to do routinely.? Thermal effects, non-perfect mechanics, carrying the mount and the SLW back-off screw setting can all cause this.? Counterweighting can mitigate the presence of backlash, which you will probably never be able to fully eliminate.

On 12/27/2023 10:54 PM, Ryan Noonan via groups.io wrote:

Much like collimation on a reflector telescope, SLW adjustments should be something every owner should be comfortable with. Like Jim W. Said, being a new mount it should be pretty close to adjusted so the adjustments will likely be very small if at all. If one owns this mount for many years one will adjust the worm many times.

Not necessarily.? When my GM811 was new it had very significant DEC backlash very much like the OP was describing.? You could see the DEC axis rotate back and forth when you gently torqued the DEC axis by hand.? I went several rounds with Brian, who basically said "just take it out under the stars and see how it does".? That did not make sense.... backlash is backlash and while an unbalanced load might bias the gears so the backlash is minimal, this will change drastically with pointing direction.

In the end I took matters into my own hands and did the worm adjustment procedure per Scott's video.? This improved things quite a bit but I could never get below about 2500mS as measured by reversing DEC at guide speed and observing when the scope actually started to move.? It was also very inconsistent.... one night the backlash reported by PHD2 would be very low (like a couple hundred mS) and the next night it would be back around 2500mS.

The backlash also had a tendency to slowly increase beyond 2500mS over a period of days to weeks.? Repeating the worm adjustment procedure would bring it down again (but still never below 2500mS). But this is a pain because it requires partial disassembly of the DEC assembly to allow rotating the worm manually.

After MUCH experimentation and head scratching, I discovered that on my mount, on both the RA and DEC axes the hole in the baseplate where the left worm block pivots was oversized (or perhaps the worm post was undersized).? This allowed the entire worm assembly to move laterally enough to feel it if I laid my finger in the "V" between the gearbox plate and the worm cover and torqued the axis.? ANY movement here translates directly into additional backlash that cannot be adjusted out.

This contributor to the backlash is not adjustable but IS fixable. However, it requires a fairly simple (and reversible) modification and I believe that is off topic for this mail list?

the last thing you want to experience is a worm gear chattering across the ring gear as the spring tension is reduced, thereby deforming your precision brass ring gear… forever. It isn’t rocket surgery, just watch the video, follow along, and go slow the first few times.

That is not possible if the worm spring bolt is properly tightened to Losmandy specs because it also acts as an out travel limiter.? I simply turn it in until it bottoms on the worm post and then back it off 1/2 turn.? That puts the spring compression pretty close to the 8mm figure I got from Brian and also prevents the worm from being forced out of engagement.? Note that before I discovered this, one night I pushed the tube with the clutches locked down tight and the RA worm skipped a couple teeth.? That one cost me $100 ;)? On the up side, the replacement worm has un-measurable 240 second periodic error.

Paul G.

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Paul Goelz
Rochester Hills, MI USA
pgoelz@...
www.pgoelz.com