On 6 Jun 2005 06:32:47 -0700, Edmund Lewis wrote in
roups.com

The lunar nodal cycle has a length of 18.6 years

Is that the interval between the moon's being in the exact same place
in the sky, the same declension or something completely different?

Yes, I think you are very much along the correct lines. It is a measure of
the movement of the apparent angle of the moon above and below the earth's
equator during its monthly orbit. So it is linked with the angle between
the earth's orbital path and that of the moon (relative to the earth).
That angle increases for about 9 years and then decreases again

It reached a low point back in March 1997 and will reach a peak in March,
next year.

See:
http://www.webspace4me.net/~blhill/p...decl.1900.html

--
Mike 55.13°N 6.69°W Coleraine posted to uk.sci.weather 06/06/2005 16:01:34 UTC