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Old 02-08-2015, 10:59 AM
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OzEclipse (Joe Cali)
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Join Date: Jun 2012
Location: '34 South' Young Hilltops LGA, Australia
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Quote:
Originally Posted by Steve_C View Post
How accurate does the curved rod need to be? I have bent it as close as I can to the correct radius for an M6 rod, 9".

How accurate does the measurement from the hinge to the rod need to be? within 1mm, .5, 2?



steve
Hi Steve,
A 1mm error in the radius, that is where the radius error results in a 1mm greater radius than the ideal radius will result in a drive rate error of 4 arc sec per minute. This is not significant for short exposures on wide angle lenses. Up to 2 min exposures up to 100mm lenses. Accurate polar alignment will present a bigger problem than this error.

Cheers

Joe
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