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Gary,

I found this old post and like what I'm reading. A 6" slide rule should be 3' or better precision. I'f confirmed then I think we have a micro emergency sight reduction champion. 

Greg Rudzinski

From: Gary LaPook
Date: 2009 Jul 7, 22:06 -0700

 

The rms of 1.8 minutes using the Bygrave method is much better than
the 4.7' error level you found using the standard sine-cosine formulas
and confirms what everyone has written about the accuracy of the
Bygrave. As you point out, the longer scale on a Bygrave would result
in an even higher level of accuracy. Since you found 1.8 with just a
ten inch standard slide rule the Byrave, which has a scale 7.85 times
longer than a ten inch rule, would produce much better accuracy and
certainly no worse accuracy than the ten inch rule. So the claim of
one or two minute accuracy with a Bygrave appears to be validated and
is consistent with my own tests on my recreation of the Bygrave.

gl