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From: Robert Eno (no email)
Date: Wed May 05 2004 - 04:57:00 EDT
Good point but this was taken into account. For example, yesterday, I
came home for lunch and couldn't resist taking a quick noon sun shot.
Index error calculations were as follows:
32.'0 on 30.'6 off
Difference = 1.4
1.4/2 = 0.7
IC = -0.7
Now let's take the next confirmatory step:
32.'0 on + 30.'6 off = 62.6
62.6 - 0.7 = 61.9
61.9/4 = 15.5 (rounded up)
Actual semi diameter = 15.9
add'l error = 0.4'
In calculating my noon latitude, I used an IC of -0.7', ignoring the
other mystery error. My noon latitude differed from actual by 0.1'.
Pretty close and one could say: "fluke", but I have been getting this
kind of consistent accuracy with my sextant.
So the question is, where in the hell does this "other" error come from
and if I wanted to factor it in to my IC, how do I go about doing this?
Theoretically, the sum of my off and on readings should have been 63.6
but I got 62.6. I should know all of this by now but even someone with
experience needs to go back to the fundamentals every once in a while.
I am baffled. Additional comments welcome.
>According to the 2004 nautical almanac the semi-diameter of the sun
varies between 16.3' at perihelion to 15.8' at aphelion. Or the diameter
varies between 31.6' and 32.6', for a difference of 1.0' or 2 X 0.5'
>
>Could this be the source of the error?
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