# NavList:

## A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

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Re: Believe it or not
From: Alexandre Eremenko
Date: 2007 Jan 26, 13:43 -0800

```Here is more of the same.
January 26, GMT 20:20, sunny weather strong wind T=44(F) P=29.1in
Sun-Moon at approx 101 degrees.

Pocket Troughton ans Simms, IC=0.
GMT:                20:58:00  21:00:40  21:02:30  21:04:20  21:07:05
21:08:10
sextant reading: 101d40'   101d43'    101d41'   101d43'    101d44'
101d44'
It was immediately clear (after the third observation, and CERTAINLY
before the reduction)
that the second observation was a blunder and I decided to discard it.
Here is the sequence of errors, including the blunder (reduced with
Frank's calculator):
0.0' , 1.8' , -0.9',  0.3, 0.2, -0.3.
If one discards the blunder, the average error is -0.14, sigma=0.5, and
if one does not discard, then the average error is 0.18 with sigma=0.9.
Not bad for a 2 inch sextant:-)

Here is SNO-T, for comparison IC=-0.5, I list the errors of 11
observations:
-0.2, 0.3, 0.1, 0.4, 0.4, -0.2, -0.2, 0.3, -0.3, 0.1, -0.1 .
Average error 0.05, sigma=0.3.
The first 5 observations were made with filter number 1, and the last 6
with
filter number 2. That filter number two gives a bit smaller reading
than filter
number 1 was known to me. It is hard to tell which of them is "right".
If one computes the averages separately one gets 0.2 for the first
filter
and -0.1 for the second one. In the IC determination both filters were
used,
and average was taken.

Alex.

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