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Re: [APML] G-11; Results of gear lapping and overhaul
I tried that pricey PEC circuit, letting the ST-4 do the training. It was
really weird! It started out smoother and then, within one cycle went nutty!
I had really wild and random PE... I never bothered again...
Frank
----- Original Message -----
From: "Duncan" <dmunro@sfu.ca>
To: "Discussion of Film Astrophotography" <astro-photo@seds.org>
Sent: Thursday, January 22, 2004 5:06 PM
Subject: Re: [APML] G-11; Results of gear lapping and overhaul
> I would have thought that the PEC would smooth the error cycles. I mean,
> isnt that the whole point of having that pricely PEC circuit on your
> controller?
>
> clear skies
>
> Duncan Munro
>
> Franklin A. Holub wrote:
>
> >Hi Glen,
> >
> >After I received my second hand G-11 about three years ago I couldn't get
> >the ST-4 to guide well with exposures of more then 1 second. Finally,
after
> >about 6 months, I lapped my RA worm gear. I had 7 "massive" cycles per
worm
> >revolution of +/-8 asecs before lapping and a nice manageable curve of
+/-4
> >asecs after lapping. You can see those PE curves here...
> >
> >http://www.my-spot.com/PE-lapping.pdf
> >
> >About a year later Scott Losmandy sent me one of his "experimental" high
> >precision worm gears. It did not reduce the total PE but boy was it
smooth!
> >See...
> >
> >http://www.my-spot.com/pe.pdf
> >
> >Just a couple of suggestions. Most folks using a G-11 have the OTA on the
> >"west". Also make sure that you have the counterweights a bit heavy on
the
> >"east". That is, when you loosen the clutch, the counterweights (on the
east
> >side of the mount) drop slowly.
> >Also, I called Scott one day and asked him why my mount seemed to run
fast
> >(or was it slow?). He said that most of the time it had to do with
setting
> >the mount on the dirt or in the yard - the feet were sinking - slowly.
For
> >my next tracking run, I put the mount on my paved driveway. Sure enough,
the
> >tracking speed was near to perfect. However, for the last year, my mount
has
> >been permanently mounted, and the tracking speed is still off - go
figure.
> >
> >Anyway, now-a-days, I can track at 1200mm for 3 seconds with no more then
a
> >couple A2 or A3's per worm cycle.
> >
> >Frank
> >
> >----- Original Message -----
> >From: "Glenn Ray" <glennlray@mail.ev1.net>
> >To: "Discussion of Film Astrophotography" <astro-photo@seds.org>
> >Sent: Thursday, January 22, 2004 2:41 PM
> >Subject: [APML] G-11; Results of gear lapping and overhaul
> >
> >
> >
> >
> >>For Y'all's Info:
> >>
> >>Well, after some reassuring advice from Dan Norman, Stu Travelbee,
> >>and Richard Crisp (THANKS, Guys!), I decided to lap the RA gear
> >>myself (gulp). I used 1 micron Luster-Lap (from McMaster-Carr);
> >>ran the drive at 16x for 4 revolutions. Also re-lubed all needle
> >>& thrust bearings.
> >>
> >>My previous PE was +/- 8", with strong swings >4 arcsec/sec. This
> >>made it difficult to guide at anything less than 2x, or very short
> >>exposures.
> >>
> >>Last night I ran a preliminary tracking test (ST-4, guiding at
> >>2032mm and tracking stars near meridian/equator). I used CCDTRACK
> >>to record the tracking data (it outputs to a log file) and plugged
> >>the results into Excel.
> >>
> >>Summary:
> >>1) Total PE has been reduced to +/- 4 arcseconds.
> >>2) Each revolution of the worm (4 mins) has three cycles of error
> >>with peak-to-peak of about 4-5 arcseconds each.
> >>3) There is a total RA drift about 75 arcseconds per hour (too
> >>fast).
> >>
> >>While I'm happy about cutting the overall PE in half, I'm
> >>perplexed about the other two findings. I can't imagine a
> >>physical scenario that would cause the quick cycles. Because I
> >>only did a rough drift alignment (N-S okay, but E-W a little off),
> >>I wonder if RA showed a component of that alignment error.
> >>
> >>I really suspect both are related to electronics, but can't
> >>confirm that until I do another run. I noted several people on
> >>the Internet who noted similar RA drift, but no answers.
> >>
> >>After performing a second run, I plan to post an article with
> >>procedures and results on my website. I also will investigate
> >>using PEC to try and smooth it further. I will welcome any
> >>suggestions or additional information.
> >>
> >>Thanks,
> >>
> >>Glenn Ray
> >>Cypress, TX
> >>http://users3.ev1.net/~glennlray/Astro
> >>
> >>
> >>
> >>
> >>
> >>>>>----- Original Message -----
> >>>>>From: "glennlray" <glennlray@mail.ev1.net>
> >>>>>To: <astro-photo@seds.org>
> >>>>>Sent: Wednesday, January 07, 2004 2:28 AM
> >>>>>Subject: [APML] Semi-OT: Precision Machine Shops in Houston
> >>>>>
> >>>>>
> >>area?
> >>
> >>
> >>>>>
> >>>>>
> >>>>>>I am considering having the RA gear on my G-11 lapped and am
> >>>>>>
> >>>>>>
> >>looking
> >>
> >>
> >>>for a
> >>>
> >>>
> >>>>>good precision machine shop in the Houston, Texas area. I may
> >>>>>
> >>>>>
> >>consider
> >>
> >>
> >>>>>companies outside of Houston if none can be found here. I
> >>>>>
> >>>>>
> >>don't think I
> >>
> >>
> >>>can
> >>>
> >>>
> >>>>>lap the gear myself, unless someone here convinces me I can.
> >>>>>
> >>>>>
> >>>>>>Please reply off-list.
> >>>>>>
> >>>>>>Thanks,
> >>>>>>
> >>>>>>Glenn Ray
> >>>>>>http://users3.ev1.net/~glennlray/Astro
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>_______________________________________________
> >>>>>>Astro-Photo mailing list
> >>>>>>Astro-Photo@seds.org
> >>>>>>http://seds.org/mailman/listinfo/astro-photo
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>
> >>>>>
> >>>
> >>>
> >>________________________________________________________________
> >>Sent via the EV1 webmail system at mail.ev1.net
> >>
> >>
> >>
> >>
> >>_______________________________________________
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> >>Astro-Photo@seds.org
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> >>
> >>
> >>
> >
> >
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> >
> >
> >
>
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