This seems to be the same problem that I am facing. I am going to try and
align my fork arms et all..but maybe i have a lemon scope too!!
-Adi

On Sun, 3 Jun 2001, John Teel wrote:

> Bruce,
>
> Thanks for the ideas. I will do a detailed systematic analysis of the goto accuracy some time in
> the next week and present the results here. Hopefully from that someone can help find a solution.
> As Doc had stated it seems as if there is something distorting the scopes perception of the
> celestial sphere since the encoders/computer seems to be working fine because it accurately
> returns to the sync stars. And yes, if I resync on a new star then I can accurately goto that
> star but not the original alignment star anymore.
>
> John
>
> > writes:
> >
> > << To me that says
> > the encoders and drives are working perfectly; however, I don't understand
> > why
> > the accuracy is so good for the alignment stars (or any star I sync on) and
> > others be so far off. Any ideas on this one? >>
> >
> > John,
> >
> > By now, you've probably figured out why a star that you sync on stays so
> > accurate, but just in case, I'll toss out a thought. If you sync on, for
> > instance, Arcturus, then slew to another star, unless you then sync on the
> > new star, the scope is still 'in step' with where Arcturus is. Since, as
> > you've found out already, you can return to that star you synced on, it shows
> > that the calculation to/from it is fine. If you were to sync on the 'new'
> > star, Vega, for instance, you'd no doubt find that you couldn't return to
> > Arcturus correctly.
> >
> > I might suggest that what you try is to sync on a particular star, then begin
> > to goto various stars, as you've been doing. But now, extend the 'goto'
> > pattern outward from your sync star a bit at a time, and perhaps only in one
> > direction at a time.
> >
> > The idea I'm getting to is to write down which direction(s) you are off when
> > you get to the star. Is it, for instance, always too far or not far enough
> > in RA as you go East or West? Does the amount change as you extend out a bit
> > further in your goto? How about the Dec? Is it going too far North or South
> > as you go to these stars? Is it, for instance, not far enough North when you
> > go Northeast? Too far East, as well?
> >
> > As you can see, what I'm getting at is to try to find what, if any, pattern
> > develops for the various directions you goto. A simple example is, if you
> > aren't orthagonal, you'll no doubt find that the further your seeks are from
> > your reference star, the greater will be the error in, say, a Dec direction.
> >
> > Anyway, it's a thought. What is really needed, it seems, is to know more
> > about the error and directions. Perhaps then, we could help in figuring out
> > where your problem lies. And just to make it easier on us (at least, for ME
> > <G>) , perhaps just use the same reference star as you return to it and then
> > expand out in distances and directions, recording the direction and amount of
> > the errors.
> >
> > Just a thought for what it's worth.
> >
> > Bruce Johnston
> >
> > Bruce Johnston Computing
> > <http://members.aol.com/bjohns7764>
> > Internet home for "SuperFix" and "MegaFix" image processing software.
> > Personal page: <http://members.aol.com/ccdastro>
> >
> >
>
>
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