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Old 08-07-2013, 09:21 PM
gary
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Join Date: Apr 2005
Location: Mt. Kuring-Gai
Posts: 5,999
Quote:
Originally Posted by Merlin66 View Post
gary,
Thanks for the input.
How do you actually measure (other than with micrometers etc) the NP error independantly from the CH error?
Hi Ken,

You are most welcome.

We ourselves take a numerical analysis approach to unraveling NP from CH and
for that matter, we simultaneously unravel other errors, such as polar misalignment,
declination axis flexure error, tube flexure, eccentric bearing errors and so on.
We do this by way of a star pointing test where we sample stars across the sky
and tabulate their catalog RA/Dec positions against their RA/Dec positions as
computed by the telescope computer.

With regards the hour angle components of CH and NP, CH is constant for
all values of Dec whereas NP is zero at the equator and reaches a maximum at
the pole. The GIF animations on our web site attempt to illustrate this -
http://www.wildcard-innovations.com....nt_errors.html

Surveyors that used the old optical theodolites had to remove errors caused
by non-orthogonal axes as well.
Here are a couple of pages for interested readers on theodolite error and adjustment -
http://whistleralley.com/surveying/theoerror/
http://whistleralley.com/surveying/theoadjust/

Best Regards

Gary Kopff
Managing Director
Wildcard Innovations Pty. Ltd.
20 Kilmory Place, Mount Kuring-Gai
NSW. 2080. Australia
Phone +61-2-9457-9049
Fax +61-2-9457-9593
sales@wildcard-innovations.com.au
http://www.wildcard-innovations.com.au
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