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Re: Improving Go-To accuracy - Fixed!

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  • johansea
    Gday Dan Dick answered most but i will add the following Doing a Polar onestar assumes you are well polar aligned ( as you mechanically centred on Sig Oct,
    Message 1 of 31 , Jun 1, 2008
      Gday Dan

      Dick answered most but i will add the following
      Doing a Polar onestar "assumes" you are well polar aligned
      ( as you mechanically centred on Sig Oct, right???? :-) )
      If you just hit enter at this stage, and goto the second star
      unclamping the axes will have no effect whatsoever,
      it wont hurt, but it wont help.
      If you KNOW you are well polar aligned, a onestar should give
      excellent results with gotos, so if you are getting big errors
      there's something else in the room.

      Are you starting from scratch each time or unparking???
      If unparking, the residual park related errors may be cutting in.
      I will be posting a new ver of my app that shows all this data
      and allows you to clear it soon.
      It only works for 4.2g, so if you are using 4.2g, i can get you a
      prelim copy to see what yr stored data is
      If its bad, we can clear it and you can retry to se what it does

      Andrew Johansen Melbourne Australia

      --- In LX200GPS@yahoogroups.com, "Daniel Calleja" <dcalleja@...> wrote:
      >
      > Hi all,
      > At the risk of keeping this thread going and asking what may be
      > obvious; can I assume that the same procedure will work on a one star
      > polar align? and is the one star EASY align of any use?
      >
      > I've been tearing my hair out trying to work out why my GOTO's were
      > way off. Andrew - I see you're on the ball as usual picking the bugs
      > and letting us all know - Thanks.
      >
      > Dan
      >
      > --- In LX200GPS@yahoogroups.com, "Derek" <schmeah@> wrote:
      > >
      > > So I tried it last time out...unlocking the clutches and manually
      > > centering the first alignment star. It worked like a charm. Every
      > > subsequent go to was dead center in the finder, and within the fov
      > of
      > > my CCD chip. I didn't think it would be so simple. Thanks again,
      > > Andrew, and all who replied.
      > >
      > > Derek
      > >
      > >
      > >
      > > --- In LX200GPS@yahoogroups.com, "johansea" <johansea@> wrote:
      > > >
      > > > Gday Derek
      > > >
      > > > --- In LX200GPS@yahoogroups.com, "Derek" <schmeah@> wrote:
      > > > >
      > > > > Thanks Andrew, but just to make sure I'm understanding you
      > > correctly,
      > > > > when I initiate a two star alignment, after the scope slews to
      > > the
      > > > > first alignment star (it will be off in the lower right
      > quadrant
      > > of
      > > > > the finder), I should unlock the RA and DEC clutches and center
      > > the
      > > > > star in the finder
      > > >
      > > > Actually, centre it in yr main EP, not the finder
      > > > Its quite easy to move the OTA at this precision manually.
      > > >
      > > > > by manually moving the OTA? Then the second
      > > > > alignment star should be closer to center than it would have
      > been
      > > had
      > > > > I centered the first star with the handbox?
      > > >
      > > > Assuming your polar alignment is good, yes.
      > > >
      > > > In altaz, the scope does an internal synch on the first star
      > > > hence the second is normally pretty good.
      > > > In polar, they dont synch on the first star, and i believe this is
      > > > part of what introduces errors if the first star is a long way off
      > > > By centering the first star manually, you avoid this problem.
      > > > Caveat, if your polar alignment is off, the second star may not
      > be
      > > in
      > > > the ep, but the internal math should work correctly, and gotos
      > shld
      > > > still be good.
      > > >
      > > > Andrew Johansen Melbourne Australia
      > > >
      > > >
      > > >
      > > > >
      > > > > Derek
      > > > >
      > > > >
      > > > > --- In LX200GPS@yahoogroups.com, "johansea" <johansea@> wrote:
      > > > > >
      > > > > > Gday Dick/Derek
      > > > > >
      > > > > > Just a clarification, as this problem has several facets.
      > > > > > If you do not park, then the reset etc isnt required.
      > > > > > Just slew to the first star by declutching and manually
      > > centering
      > > > > best
      > > > > > as possible. Then fine centre with the Hbx.
      > > > > > If yr polar align is good, the second star will be in the EP.
      > > > > > Ie no matter what the internal data settings are, if the
      > first
      > > star
      > > > > is
      > > > > > a long way off in polar twostar, it upsets the calcs, but its
      > > only
      > > > > if
      > > > > > you park, the ongoing problems cut in.
      > > > > >
      > > > > > Also
      > > > > > --- In LX200GPS@yahoogroups.com, "autostaretx" <rseymour@>
      > > wrote:
      > > > > >
      > > > > > > To clear the bad data, you can either do a Setup/Reset (a
      > bit
      > > of
      > > > > > > overkill), or the following: without removing from the
      > wedge,
      > > > > > > select Alt/Az mounting. Then "do" a one-star alignment
      > (i.e.
      > > > > > > let it think it's doing an Alt/Az one-star... you can have
      > the
      > > > > > > axes unclamped to avoid any physical motion). Once it's
      > done
      > > > > > > with that (just tap [enter] for the star, i use Alcor),
      > > > > >
      > > > > > <insert>
      > > > > > PARK, then reboot,
      > > > > > <insert>
      > > > > >
      > > > > > > set the scope -back- to Polar mount. Turn it off,
      > > > > > > clamp as you wish,
      > > > > > > turn it on, and perform a One Star alignment.
      > > > > > > Things should be better.
      > > > > >
      > > > > >
      > > > > > > > If I moved the mount instead of the using the handbox in
      > > order
      > > > > to
      > > > > > > > center the first alignment star, might this improve the
      > > > > accuracy?
      > > > > >
      > > > > > Yes ( significantly in my case when i tested it )
      > > > > >
      > > > > > Andrew Johansen Melbourne Australia
      > > > > >
      > > > >
      > > >
      > >
      >
    • dcalleja
      Thanks Andrew - WCS is not a bad little tool. I ll try your suggestion next time I m out Regards Dan HYPERLINK
      Message 31 of 31 , Jun 2, 2008
        Thanks Andrew - WCS is not a bad little tool. I'll try your suggestion next
        time I'm out


        Regards
        Dan
        HYPERLINK
        "http://www.users.bigpond.net.au/calleja/"http://www.users.bigpond.net.au/ca
        lleja/

        -----Original Message-----
        From: LX200GPS@yahoogroups.com [mailto:LX200GPS@yahoogroups.com] On Behalf
        Of johansea
        Sent: Monday, 2 June 2008 11:27
        To: LX200GPS@yahoogroups.com
        Subject: [LX200GPS] Re: Improving Go-To accuracy - Fixed!



        Gday Dan

        --- In HYPERLINK
        "mailto:LX200GPS%40yahoogroups.com"LX200GPS@..., "dcalleja"
        <dcalleja@..-.> wrote:
        >
        > Andrew
        > I start from scratch each time and do a drift align
        > (I use a little German tool to help with that).

        Another WCS user ;-)

        > Sometimes it's pretty good, other times.....
        > So I suspect my problem is a not so good alignment
        > resulting in poor gotos. And yes I have 4.2g.

        Hmm, as long as you arent parking, i would suggest you try using the
        two star method instead, as that does correct for polar misalignment
        if done in a set sequence, and you dont park.
        As per the prev threads, if the first star is off, manually centre it,
        then centre the second as per usual with the HBx.
        Note, If the second star isnt inside the 26mm ep after the slew using
        this process, yr align is off, but the system should account for it
        relatively well.

        Andrew Johansen Melbourne Australia






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