NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Lat and Long by moon transit.
From: Jeremy C
Date: 2011 Jan 28, 11:06 -0500
From: Jeremy C
Date: 2011 Jan 28, 11:06 -0500
I attempted a moon fix around transit during my big cruise in
2009. It worked okay.
I once did a Lat/Long at transit for Venus during the day. The
Longitude actually came out better than the Latitude, but that was probably an
anomaly.
The moon is a fickle creature and not for the newly initiated in Celestial
Navigation.
Here's moon data if anyone wants to play (I'm not sure if I ever posted
this one.) As you can see we are moving at a decent speed near South so
there will be a displacement of the curve. The declination is about 7
degrees south and increasing by about 14 minutes/hour so the displacement should
be somewhat minimized.
Moon Lines near Transit | Crs | 193 True | ||||
Spd | 13.5 knots | |||||
Date: | 30-Jun-09 | 1900 | DR Lat | 21-58' North | ||
GMT Hour | GMT Minute & Sec | HS deg | HS minutes | DR Long | 130-08' E | |
09 | 39-40 | 55 | 18.8 | 1900 | GPS Lat | 21-48.7' N |
09 | 40-25 | 55 | 20.1 | GPS Long | 130-07.5E | |
09 | 41-05 | 55 | 20.6 | |||
09 | 41-37 | 55 | 21.6 | Ht eye | 107 ft | |
09 | 42-08 | 55 | 21.8 | IE | 0.8 on | |
09 | 42-45 | 55 | 22.3 | all shots upper limb | ||
09 | 43-21 | 55 | 23.4 | |||
09 | 44-38 | 55 | 24 | |||
09 | 45-18 | 55 | 24.6 | |||
09 | 45-58 | 55 | 24.8 | |||
09 | 47-06 | 55 | 25.3 | |||
09 | 47-38 | 55 | 25.2 | |||
09 | 48-15 | 55 | 25.6 | |||
09 | 48-51 | 55 | 27.5 | |||
09 | 49-24 | 55 | 26.8 | |||
09 | 50-00 | 55 | 27.5 | |||
09 | 50-34 | 55 | 27.2 | LAM | ||
09 | 51-19 | 55 | 27.2 | LAM | LAM by calc | |
09 | 51-45 | 55 | 26.8 | |||
09 | 52-28 | 55 | 26.9 | |||
09 | 52-59 | 55 | 26.5 | |||
09 | 53-48 | 55 | 26.8 | |||
09 | 54-19 | 55 | 26.8 | |||
09 | 54-52 | 55 | 26.1 | |||
09 | 55-19 | 55 | 25.6 | |||
09 | 55-53 | 55 | 24.8 | |||
09 | 57-13 | 55 | 24.5 | |||
09 | 57-50 | 55 | 25.1 | |||
09 | 58-37 | 55 | 23.2 | |||
09 | 59-23 | 55 | 22.8 | |||
10 | 00-00 | 55 | 22.4 | |||
10 | 00-58 | 55 | 23 | |||
10 | 01-35 | 55 | 22.1 | |||
Jeremy
In a message dated 1/27/2011 4:36:29 A.M. Central Asia Standard Time,
jn.wilson@juno.com writes:
I discussed all this in my Navigation paper. It's at:at the bottom of page 10.The moon can be used, but my students who have tried it say, "Never again"! I've never attempted it.Jim WilsonOn Tue, 25 Jan 2011 21:49:28 EST Anabasis75@aol.com writes:The idea is pretty basic. You determine Longitude based on your measured time of LAN. The trouble is that the when you or the sun are moving N/S while shooting all of the sights, the curve of the apparent altitude is displaced a bit giving you the wrong time of LAN, there therefore longitude.The method of Lat and Long at transit works best when you are stationary and the sun is near the solstice (changing declination very little). The method works fairly well with the planets since their change of declination is usually small. It would work well with stars if you actually observe them over a long twilight. The moon is probably an exercise in futility without a computer as the declination changes fairly dramatically.You can still use the method but corrections for the various bodies' change in declination and your motion are needed.JeremyIn a message dated 1/24/2011 10:07:24 P.M. Central Asia Standard Tim, goold@vwc.edu writes:Jim,
That is not surprising, since I don't understand the effect of declination change on determination of longitude. At this point, I am abstracting from as much change as I can. I am trying to wrap my little brain around the problem of determining the longitude of my front garden. The problem of establishing the longitude of a vessel in motion is too much at this point. I would be happy to be instructed, however. That is the change you are talking about, isn't it-- the observer in motion?
Patrick
On Mon, Jan 24, 2011 at 12:23 AM, James N Wilson <jn.wilson@juno.com> wrote:
Patrick:
You still haven't shown that you understand the effect of declination
change on the determination of longitude. But you're with the majority.
Jim Wilson
____________________________________________________________
Go Back to School
Grant Funding May Be Available to Those Who Qualify
--
Dr. Patrick Goold
Department of Philosophy
Virginia Wesleyan College
Norfolk, VA 23502
757 455 3357
Charles Olson: "Love the World -- and stay inside it."
____________________________________________________________
Home Jobs (Reviewed)
We investigated work at home jobs and what we found may shock you...
News1Reports.com
Get a NavList ID Code
A NavList ID Code guarantees your identity in NavList posts and allows faster posting of messages.