> Date: Mon, 14 May 2001 13:04:04 -0700 (PDT)
> Subject: [M]: Iteration oscillation
>
> Last night I tried my hand at the iteration technique
> for polar alignment. I digested all the MAPUG topics
> on this subject and iterated using pollux (which was
> reccomended because it does not have an RA near
> polaris or polaris+12h.)
>
> I was using meade's 12mm recticle and could not get
> successive iterations that put polaris and pollux any
> closer that about 1/3 the radius of the eypiece from
> the center. Also, while slewing to m13 it wasn't in my
> 12mm Nagler, which means that whole sky accuracy was
> somewhat worse.
>
> Is this what I should expect? Is the remaining error
> mechanical?
>
> On another note, how closely related are pointing
> accuracy and tracking accuracy? Since I'm trying to
> increase exposure time, I'm willing to suffer a little
> bit on pointing if tracking is still extremly
> accurate.
>
> Any reccomendations other than "use the drift method
> instead"?
>
> John

The LX200 requires accurate polar alignment both for pointing (in polar
mode) and for tracking. There is no difference between what is required for
one than for the other.

I, too, have found the iteration method somewhat puzzling. Sometimes it
works well and sometimes it doesn't; practice just doesn't agree with
theory. (Some of the theory is on my web site.) Pollux is not *supposed*
to cause problems -- its right ascension is not near 2:30 or 14:30; it
should be a good choice.

1/3 of the radius of a 12mm eyepiece field is not bad at all. The problem
is that when you went to a different part of the sky (M13) the accuracy was
much worse.

One tactic I've found useful is to try the iterative method again, using a
star in a different part of the sky, and each time, correct only half the
error. For instance, Arcturus is a good alternative to Pollux.

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