On Tue, 31 Mar 2009 09:00:20 -0400, "Bernie Deitrick" <deitbe @ consumer dot
org wrote:

Bernie,

WOW. I knew we "wobbled" a bit, but I thought it was only of academic
interest. There is no such thing as a fixed moon period. But as you said, it
averages out over about a year. It looks like there are at least 3 'sine'
waves involved, all with a different period and amplitude. Not worth the time
to try to determine the equations for what I'm doing. 29.xxxx is good enough.

Thanks for all your help.

Chuck


Chuck,

You have to remember that the moon travels around the Earth in an ellipse, and that the Earth
travels around the sun in an ellipse as well. Also remember that according to the laws of motion,
the Earth speeds up when it is closer to the sun, and the moon speeds up when it is closer to the
Earth. Also, since the lunar cycle's length is based relative and not sidereal motion, the two can
combine to greatly shorten or lengthen the cycle length. It all averages out, of course - but see
this link:

http://www.obliquity.com/astro/lunarmonth.pdf


HTH,
Bernie
MS Excel MVP