[AZ-Observing] Re: Polar Alignment
- From: "Richard Harshaw" <rharshaw2@xxxxxxx>
- To: <az-observing@xxxxxxxxxxxxx>
- Date: Thu, 18 Mar 2010 05:57:20 -0700
A scope centered ON THE NCP and equipped with a wide enough FOV EP will show
Polaris stationary as the scope is rotated around the RA axis.
As an example, I use a Telrad to quickly pole align when in the field. I
position it on the "clock dial" position it would have for that time of
evening, placing it roughly 2/3 of the way from the inner ring to the middle
one. As a final check, I then rotate the scope about 4-6 hours in RA. If
Polaris seems to stay put between the rings, I am more or less on the pole.
Dick Harshaw
-----Original Message-----
From: az-observing-bounce@xxxxxxxxxxxxx
[mailto:az-observing-bounce@xxxxxxxxxxxxx] On Behalf Of Jack Jones
Sent: Thursday, March 18, 2010 12:44 AM
To: az-observing@xxxxxxxxxxxxx
Subject: [AZ-Observing] Re: Polar Alignment
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.
Jack
Michael Collins wrote:
> deviation from
> perpendicularity between the polar and declination axes, flexure and
> non-rigidity of the components in the optical path will all add errors.
> In general, the only one which can't easily be corrected on a typical
> commercial telescope mount is the angle between the two axes.
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