[AZ-Observing] Re: Polar Alignment
- From: Michael Collins <cal_donley@xxxxxxx>
- To: az-observing@xxxxxxxxxxxxx
- Date: Thu, 18 Mar 2010 09:35:00 -0700
On 03/18/10 00:43, Jack Jones wrote:
> Maybe I can ask my EQ mount question again, which was not satisfactorily
> answered I felt last time I asked. If you rotate the RA axis around Polaris
> (or any star for that matter) 180 degrees, will the star stay stationary in
> the field or will it inscribe a semi-circle? I would say it should stay
> stationary if the mount is perfectly orthogonal, since there supposedly
> isn't any parallax. I guess I'm asking about the orthogonality of the mount.
> I've never seen an EQ mount that didn't inscribe a circle of some diameter,
> even expensive ones or with polar finders built in.
Because Polaris isn't precisely at the pole, it will shift in position
within the field of view if the mount is aligned on the pole. It's
distance from the center of the field should remain constant, however.
The test you describe would work only if you aligned the axis of the
mount to Polaris, but even then it won't guarantee that the two axes are
orthogonal (because it might be good in that plane and off in others).
-- Mike --
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cal_donley@xxxxxxx
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