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POLAR PEC - confusing information

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  • Clay Sherrod
    Absolutely not. If you are going to operate the scope in polar mode then PEC must be done in the polar mode as well. Frankly there is absolutely no need to
    Message 1 of 36 , Sep 1, 2002
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      Absolutely not. If you are going to operate the scope in polar mode then PEC must be done in the polar mode as well. Frankly there is absolutely no need to PEC train the DEC drive for those operating in polar in the first place...the motor is inoperative except when activated via an autoguider or a user-initiated slew.

      This whole thread of aligning in Alt-Az for use in polar is confusing a lot of folks and really compounding a problem that does not exist. If you are going to use in polar, TRAIN PEC in polar; if in alt-azimuth use, the certainly use Alt-Az PEC mode to train and train BOTH drives.

      I think there is a tremendous bunch of confusion being generated here that really does not serve any purpose. The PEC training that I have done on seven scopes in Polar since the introduction of v1.3t has been excellent. It goes back to very careful and very high magnification training via either a cross hair and very dedicated attention over 3-4 spins of the worm gear (about 26 to 35 minutes total). The training can be done either visually, via remote TV screen through your digital camera (highly recommended for accuracy and ease/comfort) or CCD system.

      Folks, please do not go out here and take down your polar mounted scopes and train them in Alt-Az....this makes absolutely no sense and is very counter-productive to those who have spent a great deal of time aligning. This is one thread that needs to get back to the facts of how scopes operate; there may be a few bugs remaining in the firmware to support these GPS scopes (and yes, PEC training is NOT perfect at this time), but training for alt-az operation and then putting it in polar mode is an exercise in total futility and will lead to nothing but frustration.

      Dr. Clay


      ----- Original Message -----
      From: strongmanmike2002
      To: LX200GPS@yahoogroups.com
      Sent: Sunday, September 01, 2002 1:52 AM
      Subject: [LX200GPS] Re: PEC, Drift and Anti-backlash report: Polar


      Hi

      Have you tried training PEC in polar mode too?? How did it go? You
      indicate like I thought that it seemed to get worse rather than
      better.

      As you said, maybe we need to train PEC in Alt/Az mode for the
      corrections to work in Polar? I can't imagine why? But given the
      other "bugs" I wouldn't be surprised.

      This is a little annoying for those on a permanent polar pier!!
      Should I dissmantle my scope and lose my perfect(absolutely no drift
      in dec!) painstaking polar alignment, put it back on the tripod and
      operate in Alt/Az, train PEC then re-assemble onto wedge etc to find
      out? or might one of you with a nice light 8" or 10" like to try.....
      hint, hint.

      Dick does seem to think the PEC training in Alt/Az improved Polar
      tracking.

      Question for Dick if you are reading this. How long did you watch the
      star for when testing for Polar tracking improvement with PEC ON and
      how many diferent stars did you check it on? ie did you notice
      consistent tracking improvements? The only reason I ask is that on
      the first night of testing the new v1.3t after training PEC I
      initially thought the tracking was better but after trying different
      stars and even after "updating PEC" it was obvious that any
      improvement was absent (in fact it seemed to get worse with
      updating). Sometimes when checking tracking accuracy (without PEC) my
      scope initially gives the impression that it is tracking well only to
      start to slowly or quickly, depending on how its feeling, exhibit
      drift both periodic and in one net direction.

      I too used backlash compensation to improve the "left slew drift" but

      **** IT IS THE PPEC IN POLAR MODE I WANT....... GRRRRRR!!!****

      Maybe it is another southern hemisphere thing? You guys "down there"
      do forget about us sometimes (I get sick of hearing about bloody
      Polaris to find North.... which I have never seen!)

      Have a bonza night, throw another shrimp on the barbi and have a
      Fosters for me!

      Mike Sid on IO




      --- In LX200GPS@y..., "ralldredge2001" <ralldredge@p...> wrote:
      > In terms of Polar PEC, I'm definately with the "strongman" on this
      > issue. You claim PEC helps in polar mode. Both he and I believe,
      it
      > hurts, not helps. Perhaps the secret is in how PEC is trained.
      >
      > You trained PEC in Alt/Az. He and I both trained PEC in polar.
      >
      > So I suppose whenever I have another night to kill, I will try to
      > train PEC in Alt/Az with a renticle EP.
      >
      > Thanks for all your hardwork.
      >
      > --- In LX200GPS@y..., "autostaretx" <rseymour@w...> wrote:
      > > Hi..
      > > last night i set up on my wedge, and played with the
      > > "left slew 2 arcminute drift" syndrome, and with PEC.
      > > I was using 600x (no reticule) to monitor positions,
      > > and would use double-star targets drifting off the edge
      > > as my most precise measure.
      > >
      > > I had previously trained my RA PEC in Alt/Az, and, given
      > > my results, did not update it tonight... it was working too
      > > well to damage it. In sort: with RA PEC ON, i saw less than
      > > 4 arcsec (my approximate limit of seeing such things) drift.
      > > IF i turned RA PEC OFF, i saw immediate evidence of wander
      > > and (perhaps?) tracking error... stars would disappear off
      > > the left edge of the field of view, indicating that the
      > > scope was "falling behind" (tracking too slowly).
      > > Turn PEC back ON, and the drift stopped.
      > >
      > > Left-slew drift: I had never noticed this effect, but once
      > > told what to look for, there it was: speeds 2 or 3 would let
      > > the star drift leftward about 2 arcmin when the left slew key
      > > was released. (my field of view is 4.4 arcmin)
      > > So i increased my anti-backlash from 1% upwards...
      > > around 40% i began to see that the drift was getting shorter..
      > > now about 1 arcmin.
      > > At 82% i could see that it was -almost- stopped.
      > >
      > > At 89% it -was- stopped. No left drift at all.
      > >
      > > These settings did -not- affect the crisp operation of right slew.
      > > Right slew remained nice and controllable.
      > >
      > > One thing that getting above 80% did do was make the "kick"
      > > -audible-... i could -hear- the gears "click" as (probably)
      > > the two big nylon gears went from one-face-loaded to the other
      > > when the left slew key was released and the sidereal drive took
      > > over.
      > >
      > > SO: Polar PEC appeared to work, and anti-backlash (for me) "cured"
      > > the after-left-slew (northern hemisphere) drift.
      > >
      > > At least they did last night.
      > >
      > > have fun
      > > --dick
      > > p.s. it does still amaze me to watch the scope GoTo back-and-forth
      > > between members of multiple stars... such as Eps Lyr or Alberio..
      > > in a way it's less of a problem than GoTo between Craters,
      > > but it's still fun to watch.


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    • michaelmbauer
      Excellent report! I am happy to have read it. Thank you, Mike Bauer 8 GPS S.N. 02350 ASO Supercharge #2291-2008 42° 31 38.6 N –by– 83° 8 4.2 When
      Message 36 of 36 , Sep 2, 2002
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        Excellent report! I am happy to have read it.

        Thank you,
        Mike Bauer
        8" GPS S.N. 02350
        ASO Supercharge #2291-2008
        42° 31' 38.6" N –by– 83° 8' 4.2"
        "When it rains, let it."



        --- In LX200GPS@y..., "k_astrophotographer"
        <k_astrophotographer@y...> wrote:
        > After downloading ver. 1.3t i immediately try to do a periodic
        error
        > training with 508x. I did only the first training and no updates
        yet.
        > The results:
        >
        > 1. Before 1.3t i could take unguided images at f/3.3 with pinpoint
        > stars only at 30secs.
        >
        > After 1.3t i can take 90 and 120 secs with no problem at all(at
        > 120secs about 6 out of ten are working best) with 90secs at 90% of
        > total imaging which is good i believe.
        >
        > 2. Before 1.3t i couldn't hear any corrections from pec when
        putting
        > my ear close to the front panel.
        >
        > Now i surely can hear all the microcorrections
        >
        > 3. Pec is working at any part of the sky with the same results but
        i
        > believe that updating in different directrions will make it even
        > better
        >
        > For the record, about the guiding accuracy, the telescope tracked a
        > star at the celestial equator for 3,5 hours and the star NEVER
        > shifted away from the standart periodic error. With perfectly polar
        > aligned mount on a permanent pier this means that the shafts of the
        > telescope are perfectly vertical. The test was made with 12mm
        Guiding
        > and Astrometric eyepiece from Meade and a 2x barlow lens.
        >
        > I don't think that with the price of the system, anyone would
        expect
        > anything better. Anything worse... maybe.
        >
        > By the way, pointing accuracy is amazing on my CCD camera. 3 mins
        > maximum! with 2 standart.
        >
        > Emmanouilidis Konstantinos
        > K(A)STRO Observatory
        > 12" LX200 GPS UHTC
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