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Equipment Discussions >> Mounts

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dragonslayer1
scholastic sledgehammer


Reged: 02/25/12

Loc: SLC, UT
Re: G-11 tracking issues new [Re: blueman]
      #6145205 - 10/18/13 04:37 PM

It looks like the G-2 is the latest and greatest.. Do even the owners w/o Gemini upgrade to the servo motors anyway? I also saw where it is suggested to get the worm block upgrade? Kasey

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tomcody
Pooh-Bah
*****

Reged: 07/06/08

Loc: Titusville, Florida
Re: G-11 tracking issues new [Re: dragonslayer1]
      #6145271 - 10/18/13 05:19 PM

Quote:

It looks like the G-2 is the latest and greatest.. Do even the owners w/o Gemini upgrade to the servo motors anyway? I also saw where it is suggested to get the worm block upgrade? Kasey



The servo motors are only for Gemini users, the digital drive uses stepper motors.
The one piece block is usually only needed for imagers (who need as low a PE [periodic error] as they can get) and only to make the worm adjustments easier to do and maintain.
Rex


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dragonslayer1
scholastic sledgehammer


Reged: 02/25/12

Loc: SLC, UT
Re: G-11 tracking issues new [Re: tomcody]
      #6145283 - 10/18/13 05:29 PM

Thank you Rex,, the Losmandy seems to be in a class all by itself. Is it just the older ones that require tinkering? I also copied a statement about the motor difference, from what I got its saying the servo is an improvement?
""Servo motors run with a continuous smooth rotation, rather than discreet steps as with stepper motors.
They also have very high torque, even at high slewing speeds""
The one piece worm block would be for someone wanting what,, mabey 2-3 hour tracking? It seems that the mount can do 1-2 minute unguided pretty well? thank you,
Kasey


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Stew57
Carpal Tunnel
*****

Reged: 05/03/09

Loc: Silsbee Texas
Re: G-11 tracking issues new [Re: dragonslayer1]
      #6145328 - 10/18/13 06:00 PM

If you are pulse guiding or driving the servo via pulse ie. CGEM/DX than the statement of the difference between servo and stepper does not apply.

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tomcody
Pooh-Bah
*****

Reged: 07/06/08

Loc: Titusville, Florida
Re: G-11 tracking issues new [Re: dragonslayer1]
      #6145724 - 10/18/13 10:23 PM

Real quick:
The older G11's did not have as accurate worm gears as the newer ones and combine that with two piece worm blocks ( which have six axis of possible movement compared with two possible axis on the one piece blocks ) and you have more tinkering.
Stepper motors have a single torque out put and turn in discrete moves or steps, compared to servos which have a continous drive current and a variable current with relationship with position. This makes servos smoother for long fl imaging and able to handle positioning changes like a wind load on the ota ( when the wind moves the ota, the servo senses the position change and puts out more torque ( depending on the servo drive design) to move back to position.
Rex


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APshooter
member


Reged: 10/14/13

Loc: Camby, In.
Re: G-11 tracking issues new [Re: blueman]
      #6145871 - 10/19/13 12:00 AM

Correct. My mount was made before Gemini, it's the standard G-11 mount. I'm waiting out the clouds in hopes of testing under the stars before it gets too cold here.

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Joe Bergeron
Vendor - Space Art


Reged: 11/10/03

Loc: Upstate NY
Re: G-11 tracking issues new [Re: APshooter]
      #6145907 - 10/19/13 12:35 AM

A few days ago I examined my G11 to try to figure out why I was getting such bizarre guiding results. I made a few changes:

Added more lube to the RA worm

I found that the coupler was not correctly seated on the flat part of the stepper motor output shaft for some reason. Fixed that.

I noticed that this shaft could slide in and out of the motor gearbox a little bit. I arranged the coupler so that can't happen any more.

I loosened the RA setting circle so it can turn more freely.

Well, one or more of those things made a big difference. Tonight I set up beneath the full moon solely to try things out. Guiding was much better. The PHD graph was much gentler, with an RMS around 0.20 or slightly better. Stars are still a tiny bit elongated E-W…not sure why. Could be an issue with the PHD settings.


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APshooter
member


Reged: 10/14/13

Loc: Camby, In.
Re: G-11 tracking issues new [Re: Joe Bergeron]
      #6146692 - 10/19/13 01:19 PM

Interesting. Good to hear things are improving. I did not check my couplers to see if they were seated on the flats. I did tighten them however. Still raining here, weatherman says clearing by Sunday night! I'll try a shot or two then to see if the changes took, I'll post the results either way.

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powerstroke01
sage


Reged: 06/19/07

Loc: Western Sierra Nevada Foothill...
Re: G-11 tracking issues new [Re: APshooter]
      #6147025 - 10/19/13 04:51 PM

Well after going through double stars and elongated stars for about a year I finally sent the mount off to have it hypertuned. It came back looking brand new. After some careful balancing it now performs on par with much more expencive mounts.

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APshooter
member


Reged: 10/14/13

Loc: Camby, In.
Re: G-11 tracking issues new [Re: powerstroke01]
      #6147671 - 10/19/13 11:53 PM

Your gallery of shots using the G-11 are impressive to say the least. I hope I can get mine up to speed soon.

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APshooter
member


Reged: 10/14/13

Loc: Camby, In.
Re: G-11 tracking issues new [Re: blueman]
      #6150867 - 10/21/13 11:45 PM Attachment (15 downloads)

As promised, I have some shots from the previous night. These are quick and dirty without very much processing, but you can see the results of the tweaks. 5 subs stacked, 588 secs each. No flats or dark frames. Imaging source DMK 41AU02.AS camera.

Edited by APshooter (10/21/13 11:58 PM)


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APshooter
member


Reged: 10/14/13

Loc: Camby, In.
Re: G-11 tracking issues new [Re: APshooter]
      #6150871 - 10/21/13 11:47 PM Attachment (13 downloads)

And another shot:

Edited by APshooter (10/21/13 11:48 PM)


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APshooter
member


Reged: 10/14/13

Loc: Camby, In.
Re: G-11 tracking issues new [Re: APshooter]
      #6150906 - 10/22/13 12:08 AM

Many thanks to all who contributed info to help beat back the gremlins! I'm pleased with the results from a mechanical standpoint...it looks like the Ovision worm is a success, as were all the tweaks:
1. Swapped the Dec motor with the RA drive.
2. Readjusted the backlash on the Ovision worm.
3. Checked and tightened the Oldham couplers.
4. Put three thumbscrews in the guidescope tailpiece instead of one to hold the ST-4.
5. Balanced the mount east heavy.

Surprisingly, the biggest change came when I started shooting. I had set the backlash compensation setting in the ST-4 to 5; reducing it to 0 made the stars round. The ST-4 may have been over guiding out what was really only a small error to begin with. In any event, I'm sure the other tweaks helped the situation as well. I'm hoping to reproduce these results the next clear night. If that works I may have to start saving up for another camera


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pfile
Post Laureate


Reged: 06/14/09

Re: G-11 tracking issues new [Re: APshooter]
      #6150976 - 10/22/13 01:32 AM

how much backlash do you have on step #2? i assume you tested it by turing the worm gear with your fingers?

thanks

rob


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APshooter
member


Reged: 10/14/13

Loc: Camby, In.
Re: G-11 tracking issues new [Re: pfile]
      #6151010 - 10/22/13 02:22 AM

2mm side to side as measured at the end of the counterweight shaft. I used two .050 allen wrenches to act as spacers between the block and the RA housing. That gave me the recommended amount of backlash.

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pfile
Post Laureate


Reged: 06/14/09

Re: G-11 tracking issues new [Re: APshooter]
      #6151036 - 10/22/13 03:05 AM

2mm! surely i have more than that based on the worm play somewhere between 1/8 and 1/4 of a turn.

its a story for another thread but apparently the worm was too close to the wheel. i can't believe this.

rob


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Raginar
Post Laureate
*****

Reged: 10/19/10

Loc: Rapid CIty, SD
Re: G-11 tracking issues new [Re: pfile]
      #6151350 - 10/22/13 09:58 AM

Rob I'm really sorry about your trials. It's important to check the full motion under load when you adjust your worm mesh. Otherwise, what you describe does happen.

Have you thought about a hyper tube from Ed? I think it might behoove you to get it adjusted professionally.


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pfile
Post Laureate


Reged: 06/14/09

Re: G-11 tracking issues new [Re: Raginar]
      #6151439 - 10/22/13 10:42 AM

I think I'm just going to sell it for parts if the RA motor is burned out. this particular mount has seen too much trauma.

I was afraid to test under load thinking that the worm could be damaged. i did run it through a pretty wide range of angles and figured that the wheel should be mostly centered and in-round, but lesson learned for sure.

rob


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dragonslayer1
scholastic sledgehammer


Reged: 02/25/12

Loc: SLC, UT
Re: G-11 tracking issues new [Re: pfile]
      #6151550 - 10/22/13 11:54 AM

I have a post on getting a heavier mount (favoring the CGEM or DX) and was looking at G-11. A couple posted there that really look into the G-11 before leap,, I don't know if was a control issue or bad material batch. One specifically pointed to the 2011/2012 batch I think... Hope this helps, Kasey

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pfile
Post Laureate


Reged: 06/14/09

Re: G-11 tracking issues new [Re: dragonslayer1]
      #6151592 - 10/22/13 12:19 PM

it is possible that there was a bad run, because my experience does not match at all what i read prior to purchasing. i like to think that i researched everything and concluded that the value was there for the money, but i may have succumbed to magical thinking. i've had a lot of trouble with this mount, but i take responsibility for all my problems. i think i overestimated my ability to handle mechanical problems.

the firmware problems i've had with the G2 are another story, however

i think the bottom line is that if you own one of these and intend to use it for imaging, you need to be comfortable becoming a G11 mechanic. at the very least most people want the one-piece worm block or the ovision one-piece block. what i just learned is that you better run the worm wheel through 360 degrees of travel after replacing the worm, because there might be some high spots. to be fair we're probably talking about a tiny difference between "meshes great" and "locks up".

rob


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