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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: David C
Date: 2020 Jun 10, 03:01 -0700
Although it is just under two weeks to the winter solstice today was a perfect day for CN. The sky was blue, there was absolutely no wind and the temperature was a comfortable 14°C. I took a few practice sights using the anti-spoof app and also took a noon sight. Rather than work the noon sight or calculate intercepts for the other sights I decided to reduce an early PM sight by the ex-Meridian tables in Inmans (1932).
The meridian altitude was 51° 19' in an AH.
51° 19'
IC -4
51 15
/2 25 37.5
SD/R +14.1'
Ho = 25° 51.6 ' ----noon altitude
The PM sight was UT 01 05 46 49° 30' 50"
Following the procedure above ho = 24° 57.5' --------PM sight
Now calculate apparant time
DR long = 175° 05.2'
UT 01 05 46
195° 08.1'
increment 1° 26.5'
GHA 196° 34.6'
Add E long 175° 05.2'
LHA 371° 39.8'
- 360°
11° 39.8'
Inmans does nor have an arc to time table so I used Norie.......
Apparant time 0h 46m 40s PM
Time of noon was 01 05 46 - 0h 46m 40s = 00 19 06 which agrees with app on my phone.
Now calculate ex=meridian correction....
Table 1 9.888
Table2 8.009
Sum 17.897
From Table 3 correction = 54.2'
A second correction from table 4 is -0.2' so the correction is 54'
Finally compare the calculated correction with the actual
ho noonsight - ho pm sight = 54.1'
This remarkable agreement suggests either luck or that my errors are systematic, not random, and that they cancel out on subtraction of the two altitudes!