Navigator wrote:

Ahh Nutation? Are you perchance an astronomer?

Nope. I took an interest in prehistoric sites for a few years (less so now),
and spent some time looking into their putative astronomical alignments.
Aside from a load of solar stuff, it would seem that there was an interest
in lunar things as well.

I dicovered the nutation period quite by chance after using a planetaruim
program to animate the view of the sky from a site near me, looking in a
southerly direction. The putative alignment was too far south to be the sun
at winter solstice, and stellar observations at the horizon were discounted
due to difficulty of seeing stars through that much atmosphere, so that left
a lunar alignment as the likely candidate. As the animation ran, I noticed
that the most southerly moonrise was moving further south, approaching the
putative alignment. As it got close, I stopped the animation at each
southern standstill and noted the azimuth. Eventually, it reached a point
where it started moving north. I ran the cycle right through until it went
fully south again.

I ended up doing a bunch of reading in an effort to gain some understanding
and found out that I'd been observing the effects of the nutation period.
The site in question would appear to be aligned towards the major southern
standstill.


--
Wally
www.forthsailing.com
www.wally.myby.co.uk