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Subject: Re: [M]: LX50: Fork alignment question
From: Bill Arnett
Reply To: mapug@shore.net
Date: Fri Sep 12 00:31:18 1997

At 11:17 PM -0700 9/11/97, TheRone@aol.com wrote:
>In an effort to optimize the pointing accuracy of my Magellan II equiped 10"
>LX50, I decided to check the dec circle calibration and how parallel the
>optical tube was installed between the forks. To do this, I locked the RA at
>zero and the dec at +90 degs then centered Polaris in the eyepiece by
>adjusting the tripod legs.
>
>Now I figured that if the dec circle was out of calibration (ie: was not set
>at exactly 90 degs), this would show up as a shift in the stars position
>vertically in my eyepiece FOV (in line with the optical tube) after I rotated
>in RA from zero to 12 hrs (180 degrees)...

If I understand you correctly, then it matters not which star you point at.
If the optical axis is aligned with the RA axis then any star in the center
of the field should remain there as you rotate the RA axis. You don't
even need to use a star, a distant landmark will do as well.

But it may very well be that your whole problem is that your Dec circle is
not calibrated correctly. If the center of your field moves a little as
you rotate around the RA axis try moving the OTA in Dec a little. You will
presumably find a spot where there the field rotates perfectly around its
center. At that point, loosen the Dec circle and set it to 90 degrees. Et
voila, your scope is fine!

(Of course, there remains the possibility that your two axes are not
perfectly square. But unless you're doing long exposure photography, its
probably not worth worrying about.)

There is, I believe, a long discusson about this in the archives wrt LX200s.

---
Bill Arnett billa@znet.com http://www.seds.org/billa/
"It is better to know some of the questions
than all of the answers." -- James Thurber