NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Andrés Ruiz
Date: 2010 Mar 12, 14:29 +0100
Brad, I suppose you
first calculate Hc = f( B, L, Dec, GHA )
Refraction is a function
of the apparent altitude: R = f(Ha)
And Ha = Hc + R = Hc + f(Ha)
The solution must be obtained
with precision by an iterative process.
I have repeated the
calculations with more precise ephemerides, and the solution is the same.
Note the variation of R
with Ha:
Ha
º |
R ‘ |
30 |
1.68 |
31 |
1.62 |
32 |
1.56 |
33 |
1.50 |
Regards.
---
Andrés Ruiz
Navigational Algorithms
https://sites.google.com/site/navigationalalgorithms/
De:
navlist-bounce@fer3.com [mailto:navlist-bounce@fer3.com] En nombre de Brad Morris
Enviado el: jueves, 11 de marzo de
2010 21:24
Para:
Asunto: [NavList] Re: Star - Star
Observations
Hi Andres
Thank you very much for
sticking with me on this! I discovered that I had inverted one of the
terms in Young’s equation.
For the calculated distance
Morris
40d
21m 20.92s.
Ruiz
40d 21m 17.96s, a trivial difference between us of 3 seconds.
For the observed distance, I
now get
Corner Cosines 40d
22m 4.67s
Young’s Equation 40d 22m 4.70s
Now there is no difference
between my two results and therefore can readily retract my question about
which is better.
Corner Cosines and
Young’s Equations yield the same result.
Your result for the observed
distance is
Ruiz
40d 21m
55.26s
There is a small discrepancy
between our results of about 8 seconds.
In tracing this down, I
believe it to be the altitude correction and most likely the atmospheric
conditions
USNO
1m 36s Sirius altitude correction
1m 36s Alphard altitude correction
Morris
1m 35.47s Sirius
1m 35.79s Alphard
Ruiz
1m 33.43 Sirius
1m 33.74 Alphard
Not only have I corrected
this deficiency in the spreadsheet, I have re-cast the interface to accept GHA
Aries, SHA Object 1, SHA Object 2, Declination Object 1 & Declination
Object 2. Of course, these items will now come from the Nautical Almanac,
not my Skyscout.
Now on to the calibration of
the arc of my sextant!
Best Regards
Brad