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Equipment Discussions >> Mounts

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Raginar
Postmaster
*****

Reged: 10/19/10

Loc: Rapid CIty, SD
Re: A bit of trouble with a G11 Any suggestions? new [Re: MPT]
      #5486644 - 10/24/12 08:49 AM

Perhaps a call to Scott would help you out. From what I've read, the Losmandy guys are awesome about taking phone calls.

My guess would be the power supply as well. You'll know when you remove the RA gear cover and see if it's tracking.


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Ranger Tim
scholastic sledgehammer
*****

Reged: 03/25/08

Loc: SE Idaho, USA
Re: A bit of trouble with a G11 Any suggestions? new [Re: Cotts]
      #5486761 - 10/24/12 10:36 AM

There is no gearbox on the digital drive, just Hurst motors. But the same advice applies, check the coupler set screws for tightness on both the worm and the motor shaft.

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Startraffic
professor emeritus
*****

Reged: 02/12/06

Loc: Lat. 39.143345, Long. -77.1748...
Re: A bit of trouble with a G11 Any suggestions? new [Re: Cotts]
      #5487036 - 10/24/12 01:41 PM

Hilmi,
I had forgotten about that, & that could indeed be the trouble.

Dave,
Yup, I've got a 0-20 VDC 20A Pyramid in my POD. I set it at 18VDC for the Gemini-2. The 120VAC run from the house is ~100ft wi 12 Ga wire, the run from the PS to the mount 2 ft on 4 ga wire.

Clear Dark Skies
Startraffic
39.138274 -77.168898


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mdowns
Carpal Tunnel
*****

Reged: 06/12/10

Loc: Englewood,FL
Re: A bit of trouble with a G11 Any suggestions? new [Re: Raginar]
      #5487742 - 10/24/12 10:11 PM Attachment (18 downloads)

Problem identified,almost solved.

Many thanks to all who have replied.I did indeed call Scott at losmandy and he told me that first,the 12V,.500 amp power supply is indeed adequate for the mount.Then he suggested that I had either reversed the ra/dec connections,that the drive had been switched from N to S or I was having a balance issue. All much the same as so many of you had already suggested.Well I knew that the drive orientation had not switched so I first reversed the drive connections.This did'nt remedy the problem. Finally tonight I took the scope very slightly out of balance.After an intial shift of about half an inch to an inch of the counterweights I began adjusting them in increments of just a few millimeters.Over the course of twenty minutes of ever so slightly shifting the weights I got tracking.I've owned more gems than I can really recall including a gm8 but have never had a mount so extremely sensitive to weight.Several commentors here as well as the cnighter I bought this from had suggested this concern.I should have been more open minded.You guys were right! Tracking is not yet perfect,probably shifting a few more mils and I'll have it :-) Heres a pic of the final weight setting before I called it a night.....


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mdowns
Carpal Tunnel
*****

Reged: 06/12/10

Loc: Englewood,FL
Re: A bit of trouble with a G11 Any suggestions? new [Re: mdowns]
      #5487747 - 10/24/12 10:15 PM Attachment (19 downloads)

The air was really boiling,not allowing anything clear over 100x or so but i took a few test images with my point and shoot. Here's one.....

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mdowns
Carpal Tunnel
*****

Reged: 06/12/10

Loc: Englewood,FL
Re: A bit of trouble with a G11 Any suggestions? new [Re: mdowns]
      #5487754 - 10/24/12 10:16 PM Attachment (16 downloads)

And one more.I feel certain that with some steady air I'll get some good shots with the setup........

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Steven
sage
*****

Reged: 01/06/04

Loc: Ontario, Canada
Re: A bit of trouble with a G11 Any suggestions? new [Re: mdowns]
      #5488025 - 10/25/12 03:09 AM

Quote:

...I've owned more gems than I can really recall including a gm8 but have never had a mount so extremely sensitive to weight...




I have the same mount as yours (made for Celestron) and it is not that sensitive to imbalance. I suspect the oldham coupling is slipping. Take off the cover to confirm and if that is the case, tightening the set screw will fix it. Hope it helps.


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mdowns
Carpal Tunnel
*****

Reged: 06/12/10

Loc: Englewood,FL
Re: A bit of trouble with a G11 Any suggestions? new [Re: Steven]
      #5488135 - 10/25/12 07:31 AM

Steve,
What is the oldham coupling and under which cover can I find it? thanks!


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Startraffic
professor emeritus
*****

Reged: 02/12/06

Loc: Lat. 39.143345, Long. -77.1748...
Re: A bit of trouble with a G11 Any suggestions? new [Re: mdowns]
      #5488274 - 10/25/12 09:46 AM

Steve,
The Oldham coupler is in between the gearbox and the worm. It is under the worm cover. Looking at your mount picture, the RA worm is the rectangular box above the altitude adjustment knob. The cover is held in place by 2 small set screws (1/16th IIRC). Loosen those screws (you don't need to remove them), take the cover off & you'll see the Oldham coupler.
IIRC the allen wrench is a 0.5mm and the set screws are easily rounded out. I put a piece of WHITE electrical tape on my wrench so it would be easier to find when it gets dropped . When it does get dropped it immediately changes its' state into dark matter and becomes undetectable to any & all means of locating it, in direction proportion to its' need, raised to the power of the distance from the nearest available replacement as measured in Angstroms. DAMHIKT
FWIW The Oldham coupler is not a great design. It is inexpensive, & fairly durable in low torque situations, but it can slip, bind, or induce a harmonic stiction error if it isn't aligned well. (This stiction can & will drive you nuts if it happens to you. Completely erratic. I happened to notice the HMMV center intermittently skip.) I trimmed off a tiny piece of sprue left on mine & never happened again.
The new OPW uses a different type of coupler that works well, but really needs a solid round shaft to hold onto. The worm is fine but the gearbox has a flat spot milled into the output shaft. I made a piece of aluminum that fit on that spot & put it in. No troubles with slippage since.

Clear Dark Skies
Startraffic
39.138274 -77.168898


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Cotts
Just Wondering
*****

Reged: 10/10/05

Loc: Toronto, Ontario
Re: A bit of trouble with a G11 Any suggestions? new [Re: mdowns]
      #5488455 - 10/25/12 11:36 AM

Quote:

he told me that first,the 12V,.500 amp power supply is indeed adequate for the mount.




I'm glad you have solved your difficulty. I am, however surprised by the above. It must be true if Scott says so. If you use a 3 or 5-amp power supply with proper filtration and voltage regulation your mount's motors will be happier and you can run your dew heaters from the same power supply.

I will stand by my comments that those plug into the wall power supplies are often of minimal quality with poor regulation and filtration and that long runs of 12VDC are a poor idea..

Your moon pics are terrific, BTW.

Dave


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Steven
sage
*****

Reged: 01/06/04

Loc: Ontario, Canada
Re: A bit of trouble with a G11 Any suggestions? new [Re: mdowns]
      #5488944 - 10/25/12 04:57 PM

Quote:

Steve,
What is the oldham coupling and under which cover can I find it? thanks!




StarTraffic illustrate and explains it well. In your case, I suspect the oldham is slipping against the motor/worm shaft. After you remove the cover and with the drive on at 16x, press on RA and watch carefully whether the coupler slips.


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mdowns
Carpal Tunnel
*****

Reged: 06/12/10

Loc: Englewood,FL
Re: A bit of trouble with a G11 Any suggestions? new [Re: Cotts]
      #5489015 - 10/25/12 05:55 PM

I honestly agree with your comments. Scotts answer simply ruled out one immeadiate concern.In time,I'll definitely upgrade the power supply per yours and others suggestions.Thanks Cotts!

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mdowns
Carpal Tunnel
*****

Reged: 06/12/10

Loc: Englewood,FL
Re: A bit of trouble with a G11 Any suggestions? new [Re: Startraffic]
      #5489030 - 10/25/12 06:06 PM

Startraffic,
Thanks for all the info,insights and the pic. At least now I have something to target.It's raining here now(first rain on the telegizmo 365) so this will have to wait till tomorrow,Saturday or Sunday. I may pick your brain and Steve's again if you both don't mind.


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Steven
sage
*****

Reged: 01/06/04

Loc: Ontario, Canada
Re: A bit of trouble with a G11 Any suggestions? new [Re: mdowns]
      #5489139 - 10/25/12 07:28 PM

Quote:

Startraffic,
Thanks for all the info,insights and the pic. At least now I have something to target.It's raining here now(first rain on the telegizmo 365) so this will have to wait till tomorrow,Saturday or Sunday. I may pick your brain and Steve's again if you both don't mind.




Better to do it inside. It is more comfort and avoid loosing little parts like set screws in the dark!


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Startraffic
professor emeritus
*****

Reged: 02/12/06

Loc: Lat. 39.143345, Long. -77.1748...
Re: A bit of trouble with a G11 Any suggestions? new [Re: Steven]
      #5494741 - 10/29/12 02:20 PM

Steven,
That illustration is from the Losmandy site so I should've given credit there. Doing it inside is a good thing unless you have a clear floor outside. I have an POD so I do everything outside. The setscrews don't have to be removed, just loosened, 1/2 a turn is plenty. If they loosen on their own, then a tiny dab (I use a blunt toothpick) of the red or blue Locktite will cure that problem.

Clear Dark Skies
Startraffic
39.138274 -77.168898


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