NavList:

Bob,

If you have figured out an iterative process to gets your longitude then I think you must understand the problem fairly well already.  But I'll make a few observations that might help or perhaps not.

The essence of the problem as I see it is that the time of occultation depends on parallax.  Otherwise you could not hope to determine your position from timing the occultation.

The Nautical Almanc gives data for you to figure out time of occultation if you were at the center of the earth or at GP of Moon, ie 0 parallax.  That time would be hard enough to figure out since the occultation may not occur on the leading edge of the moon motion.  I would use a position plot to solve that, ie an analog computation.  This also points out that the time of occultation is not sufficient, we also need an estimate or rough measure of the angle between moon motion and point of occultation on the moon disc.

Now as the zenith distance of the moon at time of occultation increases, the parallax will shift the time of occultation earlier or later by an amount that depends not only on zenith distance but also where on a fixed zenith distance you are relative again to the moon direction of motion.

Both factors in the above two paragraphs imply a guess and iterative refinement approach to get analytic agreement.

My two cents.

Dave