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Re: Circular sextant?
From: Tom Sult
Date: 2017 Jul 30, 13:04 -0500
From: Tom Sult
Date: 2017 Jul 30, 13:04 -0500
Some information on the reflecting circle.
https://en.m.wikipedia.org/wiki/Reflecting_instrument#Reflecting_circles
Tom Sult, MD
Tom Sult, MD
Author: JUST BE WELL (goo.gl/jUbWIX)
Hi Bill,It's a reflecting circle. Just as you say, it looks like a sextant, and it has the same operating principle. The advantage is that it's self-calibrating, because the circular scale can be arbitrarily rotated and redundant measurements taken, permitting the target angle and the scale errors to be jointly estimated. It's bulkier for a given radius, though, and I guess somewhat more expensive too."Reflecting circle" on images.google.com pulls up a number of nice examples. I think the name of Borda is associated with the device, but I'm sure others here know more of the history.Cheers,Peter
