Would anyone here happen to have copies of the firmware binary or hex code for the EPROM's for the Losmandy dual-axis controllers? Also it is my understanding that the EPROM code for the GM-8 controller is slightly different for the G-11, as to the worm wheel tooth count differences. I am hoping to get a copy of each firmware image so I can re-program a dual-axis controller for a G-11 to work on a GM-8.

-Christopher Erickson
Observatory Engineer
Honoka'a, Hawaii
www.summitkinetics.com

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Hey there Loren,
That does help me understand a bit more; thank you.

My only additional question: Have you tried adjusting the worm block position to fit snugly on either side of the worm gear yet? or are you using the mount unadjusted as you received it??

I will have to say I need to defer a bit to other visual users, perhaps they will have more insight. As an imager I use a TVC value of zero and compensate for backlash in PHD2. When I do center visually at centering speed (for example for model building) I don't really experience what you describe as excessive springiness and my worm blocks have been snugged up well. ?I've included the TVC definition below from .

Note that the TVC value is the number of steps that the controller will compensate for backlash. Your setting of 5 (2.8 arc seconds) may (?) be too small for any noticeable difference as the setting can go all the way up to 255 steps. I might suggest adjusting the worm block position to reduce mechanical back and forth travel of the worm within the blocks so that TVC needs to work less. After that, without knowing what TVC settings you have tried, might I suggest you try larger TVC adjustment intervals? Maybe 0, then 125, then 0, then 75, then 0, then 35, etc. in order to see what gross overcorrections do to the mechanical motion??

Wish I could give you a definitive answer.
Ryan

?TVC?(Time Variable Compensation) This menu item helps compensate for the response delay caused by gear backlash when changing direction in Dec. The TVC can eliminate the hysteresis that causes this to happen. You can select a value between 0 and 255, which is the number of steps made at high speed whenever the Dec. direction is changed. You should choose a "TVC Value" that results in a short or no delay when changing the guiding direction in Dec. If you see a short jump, you have to decrease the value.

So, the number is the number represents motor steps taken at high speed when reversing DEC direction. For a G11, one step is approximately 0.56 arc seconds, so value of 50 means rotate the motor by about 28 arc seconds to take up backlash. Maximum value of 255 provides for about 143 arc seconds of backlash.

Ryan
The term "springy oscillation" describes what I see when mainly centering the scope for visual use i.e. repetitive image movement with a period of maybe less than 1/2 second.

I've observed really minor play in both RA and DEC blocks (with tight clutches), it doesn't appear to be caused by loose hardware at either worm per-se, this was tested with the CW and OTA mounted. I've adjusted Gemini's TVC factor with no improvement (currently set to value 5). I need to do more experimenting to isolate the effect I'm trying to describe, it's possible that the oscillations are occurring on both axes, maybe due to a mechanical coupling on the 30" steel pier that the mount is bolted to.

I'll try to upload a video showing centering movement using RA and DEC commands.

Loren

Hey Loren
I’m looking for further clarification if the term “springy oscillations”?

For perspective, it is difficult to troubleshoot a system with verbal descriptions that don’t match a recognized vernacular as it can introduce misinterpretation and result in misguided advice.?

The way that the spring-loaded worm works is that the worm is allowed to pivot in the worm block both toward and away from the ring gear. The spring is there to apply a constant force, pressing the worm gear into the ring gear to ensure even contact regardless of thermal expansion and minute eccentricities in the symmetry of the worm gear and the ring gear. The design of a non-spring loaded worm gear is simpler but also generally much more dependent on being properly set in the assembly process and the hit-or-miss quality you see in reviews is one result. It can work great if you get a decent sample, and you don’t want to fiddle with anything, and you don’t mind a “ship it back to the manufacturer to adjust it” approach. Many people are in this camp, and there is nothing wrong with that. We pay good money for this stuff and it is reasonable to just expect it to work ?

Losmandy mounts are designed with a different approach. They are built to last a lifetime, they are sturdy with user replaceable parts and they are designed with things like the spring-loaded worm block that reduce the performance impacts from inherently variable limits on the perfection of machined metal. This creates a mount which, while not “perfect,” can allow the user to minimize many of these variables to a great extent and achieve a mean level of performance with all other copies of the mount. There is, however, a bit of a learning curve involved.

Due to the perpendicular vector of the springs thrust against the worm/ring interface there is no situation in a properly adjusted worm block where the spring would rebound along the axis of rotation.?

Correct me if I’m wrong but what I believe you are experiencing is DEC backlash, which is normal to an extent in these mounts but also mitigated to a great extent through proper adjustment. If that is the case, you are in good company as I would bet good money that everyone on this board has dealt with it at some time.?

With the counterweights and OTA removed and the DEC clutch tightened, is there currently any back-and-forth play in the DEC axis and do you see any parts of the worm block shifting laterally while the DEC axis shifts back and forth?

Can you upload a short video that captures these variables?
1) amount of DEC movement?
2) closeup of worm block while trying to see if there is any play in the DEC axis?

That will give us more information to assist.?

Hope we can help and welcome to the group.?
Ryan

I bought a G11G last spring and thought the idea of a spring-loaded worm gear was great, as it was, my EQ6-R Pro didn't have this. I hadn't got to the point where I would see any apparent improvement as I have still yet to do any serious astrophotography. Since then, I bought an EQ8-R Pro which also doesn't have a spring-loaded worm gear. I love the completely stiff axis of those 2 EQ mounts. I am now at the point where I can evaluate the adjustable spring's worth. I find making the spring adjustment a bit fiddly and hit or miss. The wobble in the RA axis is quite noticeable which sends me down a rabbit hole of adjusting. I now realize that it is supposed to wobble a bit. I have wondered how accurate tracking can be because of this wobble. At least now I have both kinds of mounts to eventually let me know what is good or not.

I'm a new 811G owner, as of November 2023. I received the mount from Losmandy with all of the newest features: spring-loaded worm, tucked motors, Gemini 2 updates, hand-tuned by Scott. At the moment I have a heavy 130mm TOA refractor mounted with about 29 pounds of CW (11+11+ 7).

So, I am familiar with non-spring loaded worms so the observed degree of "springy" oscillations during slews or centering is really annoying. Based on my search of this problem on the user group, I was able to reduce the effect to a minimum on RA, by tedious east-loading of the counterweights. Also, I reduced centering speed to less than 10 steps, which does help. But the DEC axis has no dampening feature (namely, counterweights) that can be adjusted. So I'm currently tolerating the large oscillations on DEC. I've tried different saddle positions of the OTA, thinking an offset might reduce the effect... as of now, nothing really seems to minimize the effect.

What are my options?

I considered replacing the DEC worm spring with a stiffer spring, I am not sure that would actually dampen centering oscillations very much. I could add a? dampener counterweight but that requires a good bit of experimenting and it maybe very sensitive to OTA balance conditions. Is there some simple worm adjustment that could reduce this effect?

Loren

There are no mirror locks on a standard C11, at least not my 2006 edition.? ?Wisdom on the imaging forums is that in that case it is best to use the mirror to focus, finishing CCW to ensure engagement.??

I did find the backlash in the focus knob.? 60 steps worth.? I programmed that in to the Air.? Then came to learn it ignores that value during AF.? So with a focus step size of 50-100, and backlash of 60, it was barely moving the focuser each step.? That explains my flat curves.? A few others said to use 150 to 200 for my Increment.? ?That should hopefully get me a v curve.??

Still plan to tackle that,and maybe collimaton before worrying about tracking/guiding.? I did just print a tri bhatinov mask to aid in collimation.?

Brian

On Tue, Feb 20, 2024 at 03:56 PM, BBasiaga wrote:

Well I tried for the first time Sunday.? ?Mostly battled getting the EAF set up, a didn't clearly win.? But I got close to focus.? Amd reading up inthink I need a big step size increase in my EAF routine to improve things.? ? That'll be for the next night.?

I'm sure I need to collimate as well.?

And guiding was horrendous.? ?Almost 2 arc-s rms.? Not a clue what that is about.? ?Mount normally guides 0.6-0.8, so could have been balance or aggressiveness or min move or something.? ? Tackle that next time hopefully as well.?

Hi Brian,

I gave up on knob focusing with my C925 which was not very accurate. Plus, you have to leave the mirror locks off which invites mirror flop, especially during flips. After I changed to a Moonlite CHL inline focuser my focusing greatly improved - the mirrors stay locked, and the steps used are fine and accurate. Definitely worth the money for the quality improvement.

Your guiding could be from sky conditions or a focus issue. It's hard to say without more info.

Good luck.

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

Well I tried for the first time Sunday.? ?Mostly battled getting the EAF set up, a didn't clearly win.? But I got close to focus.? Amd reading up inthink I need a big step size increase in my EAF routine to improve things.? ? That'll be for the next night.?

I'm sure I need to collimate as well.?

And guiding was horrendous.? ?Almost 2 arc-s rms.? Not a clue what that is about.? ?Mount normally guides 0.6-0.8, so could have been balance or aggressiveness or min move or something.? ? Tackle that next time hopefully as well.?

Brian

I have a Meade 12" I use on my G11G.? The atmosphere is your enemy.? ?Mount will be fine

I had some black oxide set screws in my screw drawer this whole time. I am glad I had not ordered any yet. The factory screws were hard to get out as the allen hole was a bit too big, but they are all out and replaced. I used blue loctite. I moved the gears in a tiny bit that were rubbing the covers. If this was intentional, I can always move them out again. I left all the grease in place for this reason. I set the spring loading a bit tight and sure enough I had the RA Stall warning. I simply backed off the spring. Now on to some in house exercises.

As I was attempting to move the gears in, the allen wrench I was using was stripping out in the set screw. Also, there is some in and out play on the shaft which I guess is what is causing it to rub the cover. I am not really sure what size allen wrench is supposed to fit in these as all 4 of the set screws seem to fit the wrench differently. Some are tight and some are loose. I am going to order some new set screws from McMaster Carr, but I am trying to decide on stainless or black oxide alloy. I see the new 5-40 1/8" screws use a 1/16th wrench but none of the ones I have including the one that came with the G11 fit, they are too big. The next size down, .005 is too loose. I did manage to get the stripped one out by gluing in the wrench. That is how I conformed that it is a 5-40. I will need new grease as most is off now from the few times I have made adjustments to the worm. I don't remember what kind of grease they use for assembly, the gray stuff, but the stuff they have on the website is not gray and it is out of stock.

Your spreadsheet - and the LM video w Brian - has been a great help to me a couple of times, Edward. Thank you for the update on those settings.
Geoff

Mine don’t rub against the covers but they are covered in grease around the periphery. The grease is somewhat normal as the gears push some of it away when meshing together. Rubbing against the cover can only add to wear and tear if you ask me but thankfully it’s an easy fix, just loosen the grub screws slightly and push the gear just enough to line it up with the other one, then retighten the grub screws.

I can see that the greasy gear is not in as far as the other one is on its shaft. I can also see that the 2 gears do not line up with each other because of this slight offset. I don't see this on Losmandy's videos.

I am adjusting my worm gears and I notice that the face of the gears that are connected to the servo motor are covered in grease,?and they must rub on the cover. Is this intentional?