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Re: [APML] G-11; Results of gear lapping and overhaul
Duncan,
I didn't measure my PE with the PEC running (nor did Frank, I
believe).
While PEC definitely works at smoothing out PE, you're committed
to guiding/slewing at 0.5x from then on, which frankly, is a
pain. In that scenario, I would have to spend an extra 4-5
minutes "training" the PEC before each new target. Time's too
precious, IMO.
-Glenn
---------- Original Message ----------------------------------
From: Duncan <dmunro@sfu.ca>
Reply-To: Discussion of Film Astrophotography <astro-
photo@seds.org>
Date: Thu, 22 Jan 2004 14:06:08 -0800
>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
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>
>>>>>>
>>>>
>>>>
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>>>
>>>
>>>
>>>
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>>>
>>
>>
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>>
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