NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Andrés Ruiz
Date: 2010 Nov 29, 10:15 +0100
For Alan´s data:
|
GHA
|
DEC
|
HO
|
BO
|
LO
|
LHA
|
HC
|
Z
|
p
[º] |
p
[nm] |
|
79.062 |
8.9008 |
64.2067 |
34.655 |
-77.06 |
2.002 |
64.1804 |
184.5451 |
0.0262 |
1.572 |
|
38.5189 |
-29.5635 |
16.2217 |
34.655 |
-77.06 |
321.4589 |
16.2051 |
145.6407 |
0.0165 |
0.99 |
|
20.235 |
-3.5639 |
24.4833 |
34.655 |
-77.06 |
303.175 |
24.4502 |
113.4106 |
0.0331 |
1.986 |
Greg, Alan provided Ho,
observed, not Hs, sextant altitude. And for Jupiter the correct data is:
23/10/2010
22:54:37 UT1
ALMANAQUE NAUTICO -
NAUTICAL ALMANAC
Planet Jupiter
GHA = 20.234995 º = 20º
14.1'
Dec = -3.563867 º = -3º
33.8'
SD = 0.399345 '
HP = 0.035627 '
De:
navlist-bounce@fer3.com [mailto:navlist-bounce@fer3.com] En nombre de Greg Rudzinski
Enviado el: sábado, 27 de
noviembre de 2010 1:27
Para: NavList@fer3.com
Asunto: [NavList] Re: Accuracy of
sextant observations at sea
Alan,
You
need to include two important pieces of info- Height of Eye and Index Error.
I
went ahead and worked out the observations for a height of eye of seven feet
and zero index error using the GPS position provided.
Altair
(Dec N 8° 54.0' SHA 62° 10.1' GHA Aries 16° 53.6')
Intercept 1.5' away
Azimuth 184.5°
Formalhaut
(Dec S 29° 33.8' SHA 15° 25.8' GHA Aries 23° 05.3')
Intercept 5.0' away
Azimuth 145.6°
Jupiter
(Dec S 3° 34.0' GHA 20° 14.6')
Intercept 3.0' away
Azimuth 113.4°
Since
all your intercepts are away it looks as if you may have about 3 minutes of
index error off the arc which means that 3' can be added to each observation to
improve the plot. You will also notice that this puts your fix outside the
original triangle. When a round of observations differ in azimuth by less than
180° then it is possible that a constant error will place the fix outside the
triangle (or cocked hat).
Greg
Rudzinski
