NavList:

Stan,

An actual image of the arc and micrometer drum can't be beat. Let the student figure out I.E. from exactly what is seen on the sextant. See attached.

Greg Rudzinski

P.S. Not sure on Nav Weekend 2012. SF would work.

[NavList] Re: A celestial navigation problem
From: slk1000---com
Date: 17 Nov 2011 13:51

Greg,

As far as index error/correction goes, I tried to make it as "difficult" as possible for the students. The limb reading was between 0º and -1º, so it was definitely "off the arc". The micrometer drum reading was 58.7', so the index error was -60' + 58.7' = -1.3', for an index correction of +1.3'. I'm not sure if I can increase the clarity without giving it away, e.g. making it "on the arc". Any ideas?

It was a lower limb observation, as stated in the third paragraph of the problem.

I teach a diagram similar to yours, different only in the fact that I show only the half of the circle above the horizon. In fact, in my solution i say "Use a half diagram or similar tool to do this."

Thanks for your input.

BTW, are you going to make it to the Nav Weekend this year, or are you going to visit us electronically again?

Stan

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