Telescope Reviews: Polishing a Worm!

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Equipment Discussions >> Mounts

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blueman
Vendor Blue Sky Accessories

Reged: 07/20/07

Loc: California

Re: Polishing a Worm! new

[Re: neilson]
#5581821 - 12/21/12 02:34 AM

The worm is driven at a slew speed while engaged with the wheel and a polishing compound is applied. The lash should be set before doing this. Then when the parts are lapped in you would completely clean them and grease them and set the lash again.
Not recommended if you do not know for sure you can do this sucessfully.
Blueman

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orlyandico
Carpal Tunnel

Reged: 08/10/09

Loc: Singapore

Re: Polishing a Worm! new

[Re: gdd]
#5581825 - 12/21/12 02:39 AM

Gale, my Aeroquest worm is only +/- 8"

But it's only $100.

The only higher-precision worm that I know of for the G11 is the Ovision worm. That one is I believe +/- 3" but it costs $500-ish.

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EFT
Vendor - Deep Space Products

Reged: 05/07/07

Loc: Phoenix, AZ

Re: Polishing a Worm! new

[Re: blueman]
#5582140 - 12/21/12 09:34 AM

Quote:

The worm is driven at a slew speed while engaged with the wheel and a polishing compound is applied. The lash should be set before doing this. Then when the parts are lapped in you would completely clean them and grease them and set the lash again.
Not recommended if you do not know for sure you can do this sucessfully.
Blueman

I can tell you that this process is a complete pain. What you should do is use a couple of different lapping compounds followed by a polishing compound. Between each compound and after the final compound, everything must be completely disassembled and carefull cleaned and then reassembled. In general, for most people and mounts, this process is not worth the results.

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JohnH
Carpal Tunnel

Reged: 10/04/05

Loc: Squamish BC Moved!!!!!

Re: Polishing a Worm! new

[Re: gdd]
#5582141 - 12/21/12 09:34 AM

My mount uses a brass worm gear onto a large aluminum one.

I did a test years back to see what kind of periodic error was present by deliberately pointing the mount away from true north and letting stars drift across the film plane.

I noticed there was a weird periodic variation that damped out after about 15 minutes. I occurred to me this was due to the upper part of the worm gear getting dusty and tarnished, giving rise to a slight change in the drive rate over the course of the worm making a number of rotations, gradually cleaning itself off

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EFT
Vendor - Deep Space Products

Reged: 05/07/07

Loc: Phoenix, AZ

Re: Polishing a Worm! new

[Re: orlyandico]
#5582144 - 12/21/12 09:36 AM

Quote:

Gale, my Aeroquest worm is only +/- 8"

But it's only $100.

The only higher-precision worm that I know of for the G11 is the Ovision worm. That one is I believe +/- 3" but it costs $500-ish.

Your worm is actually a higher precision than that. It is the rest of the system that is giving you the +/- 8" accuracy. The Aeroquest worms are made to a precision of +/- 2.5 arc sec. accuracy.

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orlyandico
Carpal Tunnel

Reged: 08/10/09

Loc: Singapore

Re: Polishing a Worm! new

[Re: EFT]
#5582272 - 12/21/12 10:53 AM

Probably if you have a matched Aeroquest worm and ring gear, 5" p-p might be possible. But in my case I only have the worm.

Based on my measurements, my Aeroquest worm is really +/- 8.

this is based on isolating the fundamental on the CGEM. the 8/3 is actually much worse (about 20" p-p). Total system PE is about 40" p-p.

to be honest i don't think the Aeroquest would be +/- 2.5" - that would make them better than the Ovision and even better than the native PE of the Mach1 or AP900... which seems to stretch credulity a bit much. I'm not trashing the Aeroquest - it's $100 after all. Just being realistic.

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neilson
sage

Reged: 08/22/10

Loc: outside Pleasanton, Texas

Re: Polishing a Worm! new

[Re: EFT]
#5582317 - 12/21/12 11:27 AM

Thank you Blueman and Ed for the lesson in lapping a worm. It does sound like a lot of trouble and work.

neilson

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Charlie B
scholastic sledgehammer

Reged: 03/22/08

Loc: Sterling, Virginia

Re: Polishing a Worm! new

[Re: neilson]
#5582526 - 12/21/12 01:35 PM

I got within +-5 arcseconds with the OPB and high precision worm, which was ordered with the G11. I have no experience with the G11 without the OPB and HP worm.

Charlie B

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pfile
Carpal Tunnel

Reged: 06/14/09

Re: Polishing a Worm! new

[Re: neilson]
#5582765 - 12/21/12 04:27 PM

Quote:

Hi,
What kind of PE should be expected from a brand new G11 with Gemini 2 out of the box. From what I have read in several places about 5 arcseconds peak to peak. Can anyone verify this.
I know how to lap valves on a car when doing a valve job, but how do you lap a worm.

neilson

i was a little disappointed by mine... about +/- 16 arcseconds. the absolute value is not as important as the steepest rate of change in arcseconds/second though. that's what tests your guiding setup. unfortunately i've got 2 or 3 places on the worm where the rate of change is pretty high. even with an OAG i'm probably throwing away 35% of my subs due to oval stars.

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Geo.
Carpal Tunnel

Reged: 10/01/08

Loc: Upstate NY

Re: Polishing a Worm! new

[Re: pfile]
#5583889 - 12/22/12 11:14 AM Attachment (14 downloads)

All kind'a reminds me of Colin Chapman's (Lotus cars) early "manufacture" of a custom ratio differential for a racer. He took a stock crown from one diierental and a pinion from another, assembled them, filled the diff with metal polish and ran it until the noise stopped. Then drained, flushed, filled it with oil and went racing!

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pfile
Carpal Tunnel

Reged: 06/14/09

Re: Polishing a Worm! new

[Re: Geo.]
#5584055 - 12/22/12 12:59 PM

"i've got a chevy with a mopar cam"

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JoseBorrero
Carpal Tunnel

Reged: 09/04/09

Loc: MI

Re: Polishing a Worm! [Re: pfile]
#5586025 - 12/23/12 05:49 PM

Well, I installed my OPW-G11 with same worm, but also installed a 50mm mini guidescope with SSAG with an AT6RC f/9, getting flawless 10mins shots. I got the lowest RMS on PHD,same as using a tandem setup; ED80 and a ST80 + SSAG.

Now, I can't tell if the OPW-G11 really improve RMS on PHD as the 50mm mini guidescope was intruduced at same time. Ill have to go back using my OAG TS-9 and check.

Edited by JoseBorrero (12/23/12 05:52 PM)

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