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Sunil,

First reaction is that RA backlash should never matter when guiding: The scope should be slightly heavy eastward and the guide rate should be less than 100%.
That way the RA never reverses and hence backlash is a complete non-issue.

To debug the problem I suggest you turn off dither along with any other "feature" - when diagnosing problems the simpler the configuration the better.
It may be the fact that you have dither turned on for both axes that is causing RA backlash to show up.

Second reaction is, have you tried readjusting the RA worm? That needs to be done with the motor removed while rotating the worm by hand so you can see and feel what is going on. The worm wheel (large gear attached to the axis) needs to go through the full rotation so that you don't bind on the (unknown) high spot on the gear.

Third reaction is, I hope for your sake than when you shipped it the clutches were loose!

Best Wishes,

Mark Christensen

Hi,

? ? ? I own a ES Losmandy G11 Pmc8 variant of the Gemini2 system and I seem to have some serious RA backlash issues. I tried to get help in the ES Pmc8 forum but I was told to approach the Losmandy group. The mount is around 3 years old and I recently lubricated it using Super Lube. Guiding seems to be all over the place and most of my subs are getting discarded by SGP. The mount worked fine when it was in US but now after relocating to India(shipped via freight), it seems to have developed some serious backlash issues. I managed to fix the DEC backlash to some extend but the RA seems to be a whole different story. Appreciate any help you guys can provide. The autoguider is qhy5ll on a 200mm finder. Attaching the phd2 log. Please let me know if anyother details are needed from my end.

Sunil?

Just an update from my guiding experiments with PHD2 on Christmas Eve.
I changed over to a ZWO 120 MM mini guide camera (and this calibrated quite quickly because it is USB3).

By playing with the aggressiveness parameter in PHD2 I managed to get the RA RMS down to 0.8-0.9” and the RA Osc value to about 0.36. The DEC RMS value was slightly lower at about 0.7”. It all seems to be working now so hope to start doing some imaging now. On my first attempt with PHD2 the aggressiveness value was set too low.

I am also planning to strip the G11 down and relubricate it, and may swap the DEC and RA worms to see if that improves the periodic error.

I'll weigh in on saying mineral spirits as a general cleaner.
Wear some chemical gloves so you don't strip your hands.
Denatured Alcohol is a good rinse agent.
Again, protect your hands, and a mask or goggles is prudent. If you ever get this stuff in an eye, you won't ever forget to wear your PPE again. It hurts like hell. And a small brush can put a little pecker of it in your eye.
Then what? You've got it all over your hands and maybe arms.
Make sure you get chemical resistant brushes and bottles, and if you borrow a kitchen pan, do not return it to the kitchen.
You food will NOT taste good....

I would not use brake cleaner. Brake cleaner is really wonderful stuff. And it really cleans great. But I wouldn't want to Break my mount with Brake cleaner. ;^)
But I think it is a bit harsh for your mount parts. So me, myself, and I, would advise to stay with the more elbow grease requiring solvents.

And I like to work on the floor. The floor is my Friend.
Nothing falls further than the floor (or driveway with a tarp under).
Everything stops at the floor. Even bouncy stuff stops, eventually.

Merry Christmas!

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SonnyE


(I suggest viewed in full screen)

I have used simple mineral spirits for several different mounts without trouble.? It even dissolves the goo in Synta mounts.? I have only had to resort to brake cleaner once, for a mount with completely dried-out grease: no oil left at all.? The thickener was caked in the bearings tightly.

Be careful with brake cleaner, it is nasty stuff.

I agree with John Kmetz: full disassembly.? In addition to getting all the old lubricant and grit out and adjusting the worm mesh on reassembly there is also the opportunity to degrease the clutch pads.? The grease eventually migrates everywhere.? SuperLube is the default recommendation of many on Cloudy Nights.

Hi Jim

The Dec should be your latitude and the RA should be the current sidereal time, which is the current RA of the meridian. Do you have that available to you? Its a pretty simple calculation if not given your geographic coordinates and UT.

Jim,

Perhaps the NINA Discord forum might give you the solution you are seeking.

Best Regards,

John

Robert.Ian:

You know I just did this about a month ago and I did a full disassembly. I really wanted to get rid of the old lube and also any metal fines that accumulated when any two metal parts move against each other. Plus I had lube leakage into the clutches from the hot summer weather. If you ever have changed the oil on a new car, you may know the first drain is full of metal debris you don't want inside the engine. So I cleaned all the working parts with solvent and a brush, first gasoline then a final rinse with Brakleen.?

Reassembly went well but I would have to advise that the final tuning of the worm blocks was time consuming and bit tricky. I would suggest viewing the Losmandy videos on this before trying anything. I am pretty mechanically inclined and have a master mechanics tool set and a pretty complete workshop, but the first time around for me was a bit involved. You need to pressure the worm inward and to the left to mate the worm and ring gears, and then back off just right with the adjustment screw to stop the motor from stalling. Leftward pressure closes the gaps between the blocks and reduces sideways motion. When Losmandy says they don't recommend this at home I can see why. It takes some experience to get it just right. Too loose and you have backlash, too tight and you stall. And the margin for error in between is quite small. You probably should do a PE analysis with PEMPro or PECPrep before any work to make sure you get back to the same PE you started with.

I used the Teflon based Superlube, which is temperature resistant, and did a light coating around the whole ring gear and the worm too. The light hydrodynamic film should serve to ride over surface asperities and reduce any minor chatters. But the Teflon also serves as a barrier film to further separate higher pressure contacts. Losmandy uses that Jet-Lube MP-50 with molybdenum, which is probably overkill, but may serve to chemically react with the wear surfaces as an extreme pressure additive.? ?

So a full disassembly is best for lubrication, but you may be in for a chore to retune the worm blocks if you remove the worm to do a deep clean.

Good luck,

John

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I took my wife and kids to the "sandy hills" trails nearby to see this. We only brought binoculars and a dslr so there was no hope of a fantastic view or shot, but we had a lot of fun. Here's the shot that I got, I call it HO HO HO!

I am using the next-gen Sequencer and have an automated script.? When my targets are done for the night I want to park the OTA at the zenith so I can manually take flats.

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Jim,

Sequence Generator Pro is what I use, but I have tried NINA briefly. When I go to do flats and place my light panel over the objective I just use Park at Zenith from the Hand Controller or from the virtual HC. But you don't have this? You don't have to control from NINA. Are we missing something here :>).

Best Regards,

John

开云体育

BTW, the zenith will be Dec = latitude.?

Superb presentation and photos to boot. Top notch.

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NINA doesn't understand the Gemini-2 Home command.? I will try hour angle 0 this weekend.

Have a good holiday Brian.

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