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Subject: A-12 & Kollsman test results
From: Paul Hirose (paulhirose@XXX.XXX)
Date: Tue Jan 21 2003 - 16:07:15 EST
Results from taking 25 sun shots each with bubble sextants on my
porch. Did not use either instrument's averager. The sextants were
completely hand-held. The "correct" altitudes were obtained from the
USNO online celestial nav calculator. Index corrections for each
sextant were based on bias noted in previous sets of sights. For
timing I just glanced at my wristwatch when the sight picture looked
right. After recording all sights I corrected for watch error.
Link A-12: bias 0.0', standard deviation 1.8'
Kollsman periscopic: bias +1.5', std dev 1.4'
I used a +1.4' IC for the Kollsman; looks like I should have used
zero! Will continue to use the same IC and see if those results
continue.
The Link's results had no significant bias; apparently the +11.6' IC
I'm using is just right. I have no idea why the IC is so large. The
instrument looks near mint and the altitude mechanism feels fine.
I find the Kollsman more fun to use because it's the more
technologically complex instrument. Plus I can adjust the bubble size.
(The A-12's is bigger than I like.) However, its non-averaged results
aren't much better. But reading the altitude is a lot easier since the
minute graduations are about the same size as degrees on the A-12. I
use a magnifying glass to read that one.
Physically the A-12 is easier to manage due to its light weight and
the viewing position. You hold it in front of your chest and look down
into it. The Kollsman weighs 7.4 lb and must be held at eye level.
It's not bad, though, even on a 2-minute averaging run. The mental
effort maintaining coincidence for that long is about as tiring as the
weight.
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