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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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>>
>
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