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Lunar longitudes, not by lunar distance. Was- Re: Working a lunar
From: George Huxtable
Date: 2009 Aug 7, 16:07 +0100

Hanno Ix wrote, in 9382,

If I see things right, there must be a LOP which connects all locations
on Earth with a given, fixed difference DT between the meridian
passages of sun and moon.

What I meant is:

If I see things right, there must be a LOP which connects all those
locations
on Earth that have a given, fixed difference DT between the meridian
passages of sun and moon.

================

Is there woolly thinking here, I wonder?

Wherever on Earth the Moon is seen from, it's phase is the same except for
the effects of parallax, which can be corrected for. At Full Moon, it's
always very nearly 180 � from the Sun. So that's the Sun's lunar distance,
which is the same wherever on Earth it's observed from. And then the time
difference between meridian passages of Sun and Moon is 12 hours, the whole
World over. The phase of the Moon, the lunar distance, and the time
difference between meridian passages, change in step, going through a whole
cycle in a month, and at any moment in the month all are the same wherever
on Earth they are observed from. Measuring a lunar distance, or the time
between meridian passage (or even the phase, if it was possible to do that
precisely), all provide the same message: the time of the month. From that
time of the month, from the nautical tables, we could deduce the day (if
that was needed) or, more importantly, the time-of-day, in terms of GMT. It
by comparing that GMT with the local time that we deduce the longitude.

There's no "LOP which connects all those locations on Earth that have a
given, fixed difference DT between the meridian passages of sun and moon."
At any moment that DT is the same everywhere.

George.

contact George Huxtable, at  george@hux.me.uk
or at +44 1865 820222 (from UK, 01865 820222)
or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.

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