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Re: Altitudes, close to 90
From: Frank Reed CT
Date: 2004 Dec 1, 15:27 EST
From: Frank Reed CT
Date: 2004 Dec 1, 15:27 EST
Bill wrote:
"This thread has been a bit difficult for me to follow. Would you
please be
more specific regarding the error(s) you perceive on page 106?"
more specific regarding the error(s) you perceive on page 106?"
Sure. Bauer writes:
"Swinging an arc is also called rocking the sextant and simply means
rotating the instrument from side to side around the line of sight to the
horizon."
And that's not right, but it's a very common error. When this is done
correctly, the axis of rotation is about the line of sight to the object in the
sky. If the object is nearly straight up, that means you have to rotate the
instrument around a nearly vertical axis.
Two pages later, Bauer has two paragraphs that begin "One more wrinkle.."
(I don't have time to copy them here right now but if it would help someone
following the discussion, let me know and I will make the effort). His comments
there make it clear that he is doing this wrong. If you're observing the Sun, at
any altitude, and you "swing the arc", the Sun should remain visible right in
the middle of the field of view throughout the process. You sweep back and forth
keeping the Sun in view and line it up exactly at the low point of the
arc.
Frank R
[ ] Mystic, Connecticut
[X] Chicago, Illinois
[ ] Mystic, Connecticut
[X] Chicago, Illinois