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Re: [LX200GPS] Re: Polar Alignment and My Aching Back

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  • John Mahony
    ... The wedge doesn t have an RA axis. It adjusts alt and az (of the direction of your scope s RA axis). -John
    Message 1 of 31 , Sep 30, 2008
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      ----- Original Message ----

      > From: Gregory <docphoto52@...>
      >
      > A very big thank you to all who have replied. I think I have enough
      > information to work with now. I took the scope off the wedge last
      > night to try and get the RA axis of the wedge

      The wedge doesn't have an RA axis. It adjusts alt and az (of the direction of your scope's RA axis).

      -John

      > to work a little
      > smoother and easier. Thinking about putting teflon bearings under it.
      > Any and all advice is welcomed.
      >
      > Greg
      >
      >
      > --- In LX200GPS@yahoogroups.com, John Mahony wrote:
      > >
      > > ----- Original Message ----
      > >
      > > > From: Barry Gerdes
      > > >
      > > > Getting your base absolutely level is needed for a one star
      > alignment
      > > > in alt/azm mode but not for a two star alignment in alt/azm mode.
      > > > However when you are in polar mode you are not directly referenced to
      > > > the ground. You only need to have the telescope RA rotational axis
      > > > parallel to the earth's axis. How to do this is what the polar
      > > > alignment sequence is supposed to do.
      > >
      > > Strictly speaking, since in Meade's 1-star polar alignment method
      > you use the index mark on the base to start the scope at 0 hour angle,
      > E/W leveling will have a slight effect, since that will affect the 0
      > HA mark. So when the scope moves in RA to find Polaris, it will be
      > slightly off from where it should be. But since Polaris is so close
      > to the pole, a small error in RA/hour angle here has extremely little
      > effect.
      > >
      > > Just about any other polar alignment method will not be affected by
      > leveling. As Barry says, the point of polar alignment is to aim the
      > mount's RA axis at the pole, and that can be done whether the wedge
      > base is level or not.
      > >
      > > -John
      > >
      > >
      > > > Once this is done and made
      > > > permanent a one star alignment will be all that is necessary any
      > > > time.
      > > >
      > > > I use an accurately polar aligned permanently mounted scope and It
      > > > stays aligned for ever unless I accidently move it manually.
      > > >
      > > > Incidently my LX200GPS is too heavy to move so I made a crane to lift
      > > > it on and off the wedge. But when I do this for any maintenance the
      > > > wedge stays fixed and when the scope is replaced it only needs a one
      > > > star alignment.
      > > >
      > > > Barry
      > > >
      > > > --- In LX200GPS@yahoogroups.com, "andyhoutexas"
      > > > wrote:
      > > > >
      > > > > --- In LX200GPS@yahoogroups.com, "Barry Gerdes"
      > > > > wrote:
      > > > > >
      > > > > > Having the wedge level for a polar alignment is not necessary,
      > > > just
      > > > > > convenient. It can be degrees out as long as the final position
      > > > of
      > > > > > the telescope RA axis is parallel to the Earth's axis after
      > > > > > adjustment.
      > > > > >
      > > > > > Barry
      > > > > > Barry, I don't understand. could you explain. say my mount is
      > > > down
      > > > > 2'' to the west and 2'' to the north. how do I correct that without
      > > > a
      > > > > level. Thanks Andy
      > > > >
      > > > > > --- In LX200GPS@yahoogroups.com, Joe Bauman
      > > > wrote:
      > > > > > >
      > > > > > > I've checked my SuperWedge bubble with carpenter-type levels,
      > > > and
      > > > > > the bubble is way off. It is not mounted correctly. Now that I
      > > > have
      > > > > > an UltraWedge, I don't even use the bubble but always the
      > > > carpenter
      > > > > > level. -- Joe
      > > > > > >
      > > > > > > --- On Mon, 9/29/08, nitramcm13 wrote:
      > > > > > >
      > > > > > > From: nitramcm13
      > > > > > > Subject: [LX200GPS] Re: Polar Alignment and My Aching Back
      > > > > > > To: LX200GPS@yahoogroups.com
      > > > > > > Date: Monday, September 29, 2008, 9:28 AM
      > > > > > >
      > > > > > >
      > > > > > >
      > > > > > >
      > > > > > >
      > > > > > >
      > > > > > > --- In LX200GPS@yahoogroup s.com, "Gregory"
      > > > > wrote:
      > > > > > > >
      > > > > > > > I installed a Meade Superwedge on my pier mounted 10" LX200
      > > > GPS
      > > > > a
      > > > > > > > couple of weeks ago. The bubble level is dead center. Handbox
      > > > > in
      > > > > > one
      > > > > > > > star alignment mode. I set the dec scale to 90 degrees and
      > > > the
      > > > > RA
      > > > > > to
      > > > > > > > 0, which I read is the polar home position. (handles and
      > > > finder
      > > > > > > upside
      > > > > > > > down, front of scope pointing towards Polaris) I then center
      > > > > > > Polaris
      > > > > > > > in the center using a 9mm illuminated reticule and adjusting
      > > > > the
      > > > > > > wedge
      > > > > > > > controls until it is centered.
      > > > > > > >
      > > > > > > > The handbox says to slew in max left and right while
      > > > adjusting
      > > > > the
      > > > > > > > declination until the stars rotate around the center, or a
      > > > star
      > > > > > in
      > > > > > > the
      > > > > > > > center, stays there. Scope is still pointing at Polaris and I
      > > > > > adjust
      > > > > > > > the dec in little increments and slew left and right trying
      > > > to
      > > > > > find
      > > > > > > > true 90 degrees. Each time I adjust the dec, I bring Polaris
      > > > > back
      > > > > > to
      > > > > > > > the center using the wedge adjustments. (I generally have to
      > > > > use
      > > > > > > both
      > > > > > > > wedge adjustments to get it re-centered) So far, when I slew,
      > > > > > > Polaris
      > > > > > > > moves off center and toward the edge of field. No matter how
      > > > I
      > > > > > > adjust
      > > > > > > > dec, I can't seem to find true 90.
      > > > > > > >
      > > > > > > > Am I doing something wrong or is my set up wrong? I've spent
      > > > > hours
      > > > > > > > hunched over the eyepiece these couple of weeks and frankly,
      > > > my
      > > > > > back
      > > > > > > > and neck have had enough.
      > > > > > > >
      > > > > > > > Is there a better way to do this? Can you tell from which way
      > > > > the
      > > > > > > > star moves in the eyepiece when slewing E/W that tells which
      > > > > way
      > > > > > to
      > > > > > > > move the wedge controls? HELP!!! PLEASE...
      > > > > > > >
      > > > > > > > Greg
      > > > > > > >Greg,
      > > > > > > you might try this. i used on a lx200 classic and it worked
      > > > > great.
      > > > > > in
      > > > > > > the classic manual on page 17 paragraph b and c it outlines a
      > > > > > method
      > > > > > > for polar alignment. you can find the manual on meade's web
      > > > site.
      > > > > i
      > > > > > > have not tried on a gps scope but i will tonite. hope this
      > > > helps.
      > > > > > by
      > > > > > > the way when i used this method it took one hour to get my
      > > > > classic
      > > > > > > dead on. its still there. good luck.
      > > > > > > mike
      > > > > > >
      > > > > > >
      > > > > > >
      > > > > > >
      > > > > > >
      > > > > > >
      > > > > > >
      > > > > > >
      > > > > > >
      > > > > > >
      > > > > > >
      > > > > > >
      > > > > > >
      > > > > > >
      > > > > > >
      > > > > > >
      > > > > > >
      > > > > > >
      > > > > > > [Non-text portions of this message have been removed]
      > > > > > >
      > > > > >
      > > > >
      > > >
      > > >
      > > >
      > > > ------------------------------------
      > > >
      > > > Yahoo! Groups Links
      > > >
      > > >
      > > >
      > >
      >
      >
      >
      > ------------------------------------
      >
      > Yahoo! Groups Links
      >
      >
      >
    • Barry Gerdes
      Hi Greg and John Sorry if I was too brief in my suggestions. Giving a full ball by ball description could fill a book if all the possibilities are taken into
      Message 31 of 31 , Oct 1, 2008
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        Hi Greg and John

        Sorry if I was too brief in my suggestions. Giving a full ball by
        ball description could fill a book if all the possibilities are taken
        into account. I was as John says just trying to emphasise that there
        are two distint steps to aligning the wedge. 1. Finding true 90
        degrees for the OTA and keeping it there while the step that calls
        for it to be at 90 degrees is carried out. then 2. Carry out the
        alignment as described in the manual.

        In the Southern hemisphere I use Sigma Octans as the alignment star
        and it is much harder to find and identify than Polaris but I have
        the added advantage of a very distintive array of stars that neatly
        fill a 26 arc minute field at the south celestial pole which I use as
        a check that polar alignment is correct.

        I personally use a number of short cuts but these are too complicated
        to explain to a beginner but I will emphasize that I always do an
        orthogonal alignment on the scope before I attempt any real use of
        the telescope. Luckily Meade have changed the construction of the
        forks in their latest telescopes that makes orthogonality extremely
        good out of the box and any improvement would need a highly skilled
        engineering job to implement.

        Barry

        --- In LX200GPS@yahoogroups.com, John Mahony <jmmahony@...> wrote:
        >
        > ----- Original Message ----
        >
        > > From: Gregory <docphoto52@...>
        > >
        > > Question about 2. below... Adjust the wedge until you get true 90
        > > degrees , OR, adjust the OTA in dec?
        >
        > Barry forgot to mention in this step that you need to adjust the
        dec (that, after all, is the point of this step- you're trying to
        find 90 dec). If you're trying to get a star in the center while
        doing this, then you have to adjust _both_ the wedge _and_ the dec
        until you get the star to stay centered while rotating in RA. This
        gets _really_ confusing, trying to figure out which one to adjust,
        since the dec adjustment will look the same as the wedge alt
        adjustment in the EP (if the scope is near 0 or 12 hour angle), but
        these will have different effects on whether the star will stay
        centered when rotating in RA.
        >
        > When I was first developing the RA spin method to find 90 dec, I
        too thought that it would be convenient to have a bright star to
        focus on as the "center". But after just a few tries I quickly
        realized that this raises the complication/frustration level to the
        point where my brain was in danger of exploding, so I quit. I just
        focused on the "center of rotation", regardless of where it is in the
        star field. This is where your RA axis is pointing, so just adjust
        your dec to aim the OTA at this point (or as close as you can get
        it), for true 90. Don't adjust the wedge in this step, because then
        you're moving both the RA axis and the OTA axis simultaneously, so
        the center of the FOV and the center of rotation don't get any closer
        together.
        >
        > -John
        >
        >
        > > The directions i've been reading
        > > say to adjust the OTA in dec until you get the true 90 deg., then
        use
        > > the wedge adjustment to bring the star back to center. I'm
        confused
        > > now??? But I do appreciate the help.
        > >
        > > Greg
        > >
        > >
        > > --- In LX200GPS@yahoogroups.com, John Mahony wrote:
        > > >
        > > > ----- Original Message ----
        > > >
        > > > > From: Barry Gerdes
        > > > >
        > > > > Hi
        > > > >
        > > > > That is the general idea but not the way to do it.
        > > > >
        > > > > 1. Find Polaris or any nearby star and center it.
        > > > > 2. Adjust the wedge bit by bit till you can rotate the
        telescope in
        > > > > RA/azimuth to the a position where the Polaris stays in the
        middle
        > > > > for 360 degrees of rotation. Doing this will probably take
        most of
        > > > > the night. And if the axes are not orthogonal you will get at
        the
        > > > > best an elipse lengthened towards the forks.
        > > >
        > > > You will always get a slight elliptical motion due to fork flex
        (the
        > > forks are stiffer along the long axis of their cross-section than
        the
        > > short axis). Other than that, the motion is always circular,
        since
        > > you're rotating about the RA axis.
        > > >
        > > > If there's orthogonality error, that makes it impossible to get
        the
        > > center of rotation of the image (whether that's Polaris or not)
        to the
        > > center of the FOV, but it doesn't cause elliptical motion.
        > > >
        > > > > 3. When you get this position lock the OTA up so it can't
        move in
        > > > > respect of the forks.Becaise it is now sitting at exactly 90
        degrees
        > > > > 4. Start a full polar alignment from the position where the
        scope is
        > > > > assumend to be at 90 degrees.
        > > >
        > > > But make sure you move the RA back to 0 hour angle before
        starting
        > > the polar alignment procedure.
        > > >
        > > > > unlock the OTA and let the telescope go
        > > > > to the next stage of pointing to Polaris.
        > > >
        > > > No, leave the clutches locked.
        > > >
        > > > > 5. Center Polaris using only the Wedge controls
        > > > > 6. Complete the alignment.
        > > > >
        > > > > This should get you pretty close to polar aligned and allow
        much
        > > > > easier fine tuning. Remember if the orthogonality is more
        than two or
        > > > > three arc minutes out gotos may be erratic. Much more so than
        with
        > > > > alt/Azm alignment.
        > > >
        > > > The SMT ("Smart Mount") training in later versions of the
        > > LX200GPS/R/ACF scopes should correct for orthogonality error- at
        least
        > > for pointing. Since the only reason to use a wedge is to avoid
        field
        > > rotation in long exposure imaging, and that requires a
        mechanically
        > > correct polar alignment (ie, the RA axis aimed at the pole), and
        that
        > > can't be fixed with "computer correction", I wonder if Meade
        included
        > > the SMT correction in the polar alignment procedure, so that the
        > > procedure leaves the RA axis aimed accurately at the pole.
        > > >
        > > > -John
        > > >
        > > >
        > > > > I have tried to simplify alignment as much as possible. The
        main
        > > > > thing to remember is that finding the 90 degree point has
        nothing to
        > > > > do with Polaris' actual position. Polaris is just being used
        as a
        > > > > sighting reference for this task and the actual positioning
        is done
        > > > > with the wedge controls when the actual alignment procedure
        calls for
        > > > > it.
        > > > >
        > > > > Barry
        > > > >
        > > > > --- In LX200GPS@yahoogroups.com, "Gregory" wrote
        > > > > >
        > > > > > I installed a Meade Superwedge on my pier mounted 10"
        LX200 GPS a
        > > > > > couple of weeks ago. The bubble level is dead center.
        Handbox in one
        > > > > > star alignment mode. I set the dec scale to 90 degrees and
        the RA to
        > > > > > 0, which I read is the polar home position. (handles and
        finder
        > > > > upside
        > > > > > down, front of scope pointing towards Polaris) I then
        center
        > > > > Polaris
        > > > > > in the center using a 9mm illuminated reticule and
        adjusting the
        > > > > wedge
        > > > > > controls until it is centered.
        > > > > >
        > > > > > The handbox says to slew in max left and right while
        adjusting the
        > > > > > declination until the stars rotate around the center, or a
        star in
        > > > > the
        > > > > > center, stays there. Scope is still pointing at Polaris and
        I adjust
        > > > > > the dec in little increments and slew left and right trying
        to find
        > > > > > true 90 degrees. Each time I adjust the dec, I bring
        Polaris back to
        > > > > > the center using the wedge adjustments. (I generally have
        to use
        > > > > both
        > > > > > wedge adjustments to get it re-centered) So far, when I
        slew,
        > > > > Polaris
        > > > > > moves off center and toward the edge of field. No matter
        how I
        > > > > adjust
        > > > > > dec, I can't seem to find true 90.
        > > > > >
        > > > > > Am I doing something wrong or is my set up wrong? I've
        spent hours
        > > > > > hunched over the eyepiece these couple of weeks and
        frankly, my back
        > > > > > and neck have had enough.
        > > > > >
        > > > > > Is there a better way to do this? Can you tell from which
        way the
        > > > > > star moves in the eyepiece when slewing E/W that tells
        which way to
        > > > > > move the wedge controls? HELP!!! PLEASE...
        > > > > >
        > > > > > Greg
        > > > > >
        > > > >
        > > > >
        > > > >
        > > > > ------------------------------------
        > > > >
        > > > > Yahoo! Groups Links
        > > > >
        > > > >
        > > > >
        > > >
        > >
        > >
        > >
        > > ------------------------------------
        > >
        > > Yahoo! Groups Links
        > >
        > >
        > >
        >
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