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Playing with the almanac prior to a 4-day outing on Lake Michigan, but
missing something important.

For an my assumed location in central Indiana, I used 40d 28' N and 86d 57'
W.  Date: 22 Sept 2004.  Despite our longitude we are on eastern standard
time (no daylight savings time for most of us in Indiana.

Time of tabular moonrise is at 40N is 14:35 on 22-9-04
Time of tabular moonrise is at 45N is 14:58 on 22-9-04
Time of tabular moonrise is at 40N is 15:27 on 23-9-04

Latitude correction from Table 1 is 2 minutes (30', 5d increments, 23
minutes from 40d to 45d))

Longitude correction from Table 2 is 12 minutes (90d W, 52 minutes
difference from 22-9-04 to 23-0-04)

Added to 14:35 it comes out to 14:49, or 2:49 PM.

This way off the 15:37 my GPS, the online almanac, and other sources state.
Inspection revealed the 15:37 time to be close to reality.

Playing with the possibilities for the discrepancy, only arc-to-time for the
11d 57' from 75d (center of eastern zone) made sense.

Arc-to-time for the Sun passes my common sense test--360d in 24 hours for 15
degrees/hour.

For the stars, it would seem arc to time would be 360d in 23:56:06 so arc
would be divided by approx. 15.04d/hr to get time in solar hours.

The fine details of the Moon in relation to earth and the sun still elude me
(a subject for study this winter), so I wonder if a straight arc-to-time is
the correct way to adjust from the almanac sum to local time?

Your thoughts would be appreciated.
=================================
A more complex question--at least to me:

Regarding the Earth, Moon, and Sun I recently read (if I correctly remember
and understood it) that the Earth and Moon actually rotate--in relation to
each other, about a point 800 miles from the Earth's surface.

To draw a 2D analogy, if a 300 lb. person and a 30 lb. person were on a
see-saw, the fulcrum would have to be much closer to the large person to
achieve balance.  If we were to spin the pair around the fulcrum, in
relationship to a nearby post, each person would get nearer then farther
from the post with each revolution, the 30 lb person more so because of the
greater distance from the pivot point.

My question:  Ignoring precession and other wobbles, does the Earth's axis
go smoothly around its elliptical orbit of the Sun; or do the Earth/Moon
pair spin around some point 800 miles below the Earth's surface between the
Moon and Earth's centers, held together by gravitational attraction (like
the pair above held together by the see-saw) with each getting nearer and
farther from the Sun as they go about their journey?

Thanks

Bill

   

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