NavList:

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.

 

Jeremy

 

In 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
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