That's interesting Richard. After some discussions with Meade a few months
back I gave up trying to align the OTA after they told me that the algorithm
compensates for it. I will have to give it another try based on your
results.

Blair


----- Original Message -----
Sent: Wednesday, April 12, 2000 7:19 PM
Subject: Re: [M]: LXD 750 Mount


> Abe,
> I few years ago I had an LXD750 with a Meade 10" SCT mounted on it. I
could
> usually get about 10-15 arc minutes pointing error after a 2 star
> alignment. Using TheSky and T-Point software, the error could be reduced
to
> 1-2 arc minutes.
>
> It is not difficult to measure how close to 90 degrees the scope optical
> axis is to the DEC axis, it just takes patience! After measuring the
error,
> use metal shims to adjust the height of the back or front of the scope
tube
> , that is, raise or lower one end of the tube (assuming the way your scope
> is attached allows this).
>
> The following procedure works well and is quite easy to do with a "GOTO"
> mount. Unfortunately, it is hard to describe in words, but I'll give it a
try!
>
> With the mount polar aligned as good as you can get it using the "2 star"
> method (described in the Meade manual) or any way that works for you, find
> a star in the scope keypad catalog that is just West or just East of the
> meridian, in the south, with a DEC of around 0 degrees (DEC not very
> important). Use the "GOTO" feature to slew to that star.
>
> Then, after centering the star in a low power eyepiece, Sync the scope on
> that star. Next, find another star near the first star, but on the OTHER
> side of the meridian, then use the "GOTO" and slew the scope to this
> star(Both stars must be in the scope catalog of stars). Hopefully, the
star
> will appear somewhere in the field of the low power eyepiece. Use ONLY the
> North and South keypad buttons to place the star as near to the center of
> the field of view as possible (this does not have to be done with great
> precision). Finally, estimate how far the star is away from the center of
> the eyepiece field of view in the EAST-WEST direction --- disregard any
> errors in the North-South direction; 1/2 of this East-West angle error is
> how much you have to raise or lower one end of the tube to make it 90
> degrees (orthogonal) to the DEC axis.
>
> You will have to convert your measured angle error (in minutes of arc) to
> radians (multiply by pi/(60*180); then the required shim thickness is the
> separation between the front and rear tube mount supports (in inches)
times
> this angle in radians. You can then repeat the procedure using a medium
> power eyepiece to get a more accurate measurement and shim thickness.
>
> This technique works quite well. If you can't seem to find the correct
shim
> thickness using this technique, then there must be other sources of error,
> like mirror flop, tube-to-mount flexure, etc. I was able to greatly
improve
> the pointing of my LXD750 with the 10" SCT this way. Your 14" SCT is quite
> a bit heavier than my 10", so I would expect more errors from other
sources
> like flexure. In fact those other errors will limit how well you can
> ultimatly point the scope, unless you use something like T-Point.
>
> If my description was difficult to understand, let me know and I (or
> someone in this group) can try to clarify the procedure.
>
> Richard
>
>
>
>
>
>
>
> At 11:23 AM 4/12/00 -0400, you wrote:
> >Hello:
> >I have seen some information on how this would be done with a fork mount
> >but I'm not quite sure how I would do it with the German Equatorial. It
> >would be like tying to do the same procedure while the forks are on a
wedge
> >and tripod. Do you have any suggestions?
> >Thanks
> >Abe
>
>
>
>

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