NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Multi-Moon line exercise in 2 parts
From: Peter Hakel
Date: 2009 Aug 7, 20:54 -0700
From: P H <pmh099@yahoo.com>
To: NavList@fer3.com
Sent: Wednesday, August 5, 2009 10:01:17 AM
Subject: [NavList 9371] Re: Multi-Moon line exercise in 2 parts
From: "Anabasis75@aol.com" <Anabasis75@aol.com>
To: NavList@fer3.com
Sent: Tuesday, August 4, 2009 8:33:54 PM
Subject: [NavList 9359] Multi-Moon line exercise in 2 parts
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From: Peter Hakel
Date: 2009 Aug 7, 20:54 -0700
Backtracking the coordinates given below to UT = 10:00:00 = 1900L gives:
N 21 degrees 47.2'
E 130 degrees 04.9'
The method I chose here does not include the calculation of uncertainties. If I can find the time, I might redo this problem using the "rapid-fire fix"-type method described in my previous post.
Peter Hakel
N 21 degrees 47.2'
E 130 degrees 04.9'
The method I chose here does not include the calculation of uncertainties. If I can find the time, I might redo this problem using the "rapid-fire fix"-type method described in my previous post.
Peter Hakel
From: P H <pmh099@yahoo.com>
To: NavList@fer3.com
Sent: Wednesday, August 5, 2009 10:01:17 AM
Subject: [NavList 9371] Re: Multi-Moon line exercise in 2 parts
Jeremy,
I processed your meridional example. From the attached spreadsheet I get the UT of transit as 9:51:33 (cell F13). The altitude 55.447 degrees (decimal, in cell F1) contains corrections for vessel motion and declination change, and pertains to the instant of your last measurement at 10:01:35. Correcting this for index error, semidiameter, parallax, and refraction (using standard conditions) gives Ho = 55 degrees 32.2'. From this I obtain the latitude and longitude at UT = 10:01:35 as:
N 21 degrees 46.9'
E 130 degrees 04.8'
This longitude value is dead-reckoned by 10m 02s from the one extracted at the UT of transit (360 - GHA).
This is not in the format that you asked but I'm hoping we can still compare. I will look at this more later.
As for accuracy, I would certainly round the result to whole minutes of arc.
Peter Hakel
I processed your meridional example. From the attached spreadsheet I get the UT of transit as 9:51:33 (cell F13). The altitude 55.447 degrees (decimal, in cell F1) contains corrections for vessel motion and declination change, and pertains to the instant of your last measurement at 10:01:35. Correcting this for index error, semidiameter, parallax, and refraction (using standard conditions) gives Ho = 55 degrees 32.2'. From this I obtain the latitude and longitude at UT = 10:01:35 as:
N 21 degrees 46.9'
E 130 degrees 04.8'
This longitude value is dead-reckoned by 10m 02s from the one extracted at the UT of transit (360 - GHA).
This is not in the format that you asked but I'm hoping we can still compare. I will look at this more later.
As for accuracy, I would certainly round the result to whole minutes of arc.
Peter Hakel
From: "Anabasis75@aol.com" <Anabasis75@aol.com>
To: NavList@fer3.com
Sent: Tuesday, August 4, 2009 8:33:54 PM
Subject: [NavList 9359] Multi-Moon line exercise in 2 parts
I figured that I need to give some LOP data to reduce with all of
these people building and using their Bygrave's slide rules, and to stir the pot
a bit on the list. So in order to kill two birds with one stone, I offer
the attached Excel spreadsheet. Lying therein are a plethora of upper limb
moon LOP's which should allow eager navigators to fix the position of my
ship. There are a few features of particular note that should appeal to
certain members of the list.
1) The given DR is a real DR tracked from the AM star fix some 14
hours earlier
2) The moon is fairly close to the celestial equator (please note the LARGE
hourly change in declination)
3) The ship's track is at a fair clip and nearly Southerly.
These should be considered fairly extreme conditions to work out the
Latitude and Longitude of the ship; the first position from many LOP's away
from upper transit, and then again around the time of transit.
I will be most appreciative if people who solve the transit portion
graphically can post an image or file of their curve and to see what the
1900L fixes is. (ZD -9)
I offer the following challenges:
1) what would you calculate the local zone time of transit to
be?
2) what was the 1800L fix?
3) what was the 1900L fix?
4) what was the actual local zone time of transit by observation?
5) most critically, how much faith would you put in these fixes?
I will post the actual GPS fixes and my celestial solutions for both
times at a later time.
Have fun!
Jeremy
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NavList message boards: www.fer3.com/arc
Or post by email to: NavList@fer3.com
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