Quote:
Originally Posted by Merlin66
In Dave Trott's original article in February 1988 Sky & Telescope, p213, he shows the comparative drive error between the single and double arm barndoor designs.
For the single arm after 40 mins, the error is roughly 40 arc sec whereas for the double arm it's about 5 arc sec. I think this is a very good result.
IMHO I think polar error in set up would probably be the greatest potential error risk.
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I think the polar error is a big issue too, but not insurmountable.
While I don't dispute the theoretical accuracy of the Trott mount for tracking, what I'm not sure about is the ability to construct one within the tolerances required to achieve that level of accuracy.
It was after I read
this post on Cloudy Nights that I began to wonder. Essentially the post outlines an analysis of how an error of 2.5mm in certain dimensions will introduce enough error to make it equivalent to a basic type 1 two arm barn door mount.
On the other hand, how much tolerance does a type 1 have if you were 2.5mm out? No-one analysed that. I'm pretty sure that I could get it within 1mm, which is still better than a type 1, I guess.