# NavList:

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

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Re: Precision of lunars
From: Alexandre Eremenko
Date: 2007 Apr 15, 10:18 -0700

```Observations in March-April 2007.

SNO-T from my balcony IC=-0.5 (constant, measured at least once a
day).
Reduction with Frank's calculator, temperature and pressure was taken
into account. No correction was used for prizmaticity of filters;
after a careful investigation it was found to be less than 0.15'
for all filter combinations.
The IC actually varies a little, but this variation seems to depend on
the method of measuring IC, rather than on time. 3 or 4 years of
experience
with this sextant show that IC remains constant unless I transport it
by
car, train or airplane, or do some adjustment.
Using different methods I always obtain IC between -0.4 and -0.6 so I
use the average.

I post ALL my observations
from March 20 till now, not trying to choose the
best or the worst or "typical".

Total 85 shots of lunar distances
in 20 series (usually 4-6 each).
Average error over all shots is 0.07 (thus the systematic
bias seems negligible).
Sigma over all shots is 0.26.

Error distribution for individual shots:
41 with error less than 0.1
19 with error in the interval (0.1-0.2)
11 with error in the interval (0.2-0.3)
5 with error in the interval (0.3-0.4)
7 with error in the interval (0.4-0.5)
2 with error in the interval (0.5-0.6)
(of the total of 85)

Error distribution of series:
10 with error less than 0.1
4 with error 0.1-0.2
5 with error 0.2-0.3
1 with error 0.2-0.4.
(of the total of 20 series)

Here is the list of all series:

April 13, Sun at 53d:
0.1, -0.2, -0.5,  -0.3, -0.3;    aver=-0.24, sigma=0.22
0.1, 0.0, 0.0, 0.0, 0.2;         aver= 0.06, sigma=0.1
April 3, Aldebaran at 126d (full Moon, too bright, was not
0.4, 0.3, 0.2, 0.3, 0.2;         aver=0.28   sigma=0.08
0.3, 0.6, 0.4, -0.2, 0.6, 0.4, 0.8; aver=0.4, sigma=0.3
April 3, Pollux at 73d:
0.0, -0.1, -0.1, -0.1;           aver=-0.07, sigma=0.05
April 2, Venus at 137d:
0.3, 0.0, 0.5, 0.4;              aver=0.3, sigma=0.2
0.3, 0.2, 0.5, 0.2;              aver=0.3, sigma=0.14
0.0, 0.0;                        aver=0.0, sigma=0.0
0.1, 0.0, 0.1.                   aver=0.06, sigma=0.06
April 2, Aldebaran at 115d:
0.1, 0.1, 0.1, -0.3, 0.2, 0.0;   aver=0.03, sigma=0.17
March 29, Sun at 139d (limit of sextant scale!)
0.4, -0.5, 0.1, -0.5, -0.1;      aver=-0.12, sigma=0.4
March 29, Venus at 102d:
0.0, 0.1, 0.1, -0.1, 0.3;        aver=0.08, sigma=0.15
March 29, Saturn at 10d:
-0.1, 0.1, 0.1, 0.3, 0.1, 0.3.   aver=0.13, sigma=0.15
March 29 Aldebaran at 79d
0.2, 0.0, -0.1, 0.2              aver=0.07, sigma=0.15
March 26, Venus at 70d:
-0.2, 0.1, 0.1;                  aver=0.0, sigma=0.17
0.0, 0.1, 0.2, -0.2;             aver=0.0, sigma=0.17
March 26, Aldebaran at 42d:
-0.2, -0.1, -0.5;                aver=-0.26, sigma=0.2
March 25, Venus at 58d:
-0.2                             aver=0.2
March 21, Venus at 7d:
0.1, 0.2, 0.2;                   aver=0.16, sigma=0.06
March 21, Aldebaran at 30d:
-0.1, -0.2, 0.2, 0.1, -0.5, 0.0; aver=-0.08, sigma=0.24

Alex.

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