(SNES) An analemma dilemma

[Albireo54@aol.com]

Hi All,

I received one response to my little question about the times of earliest 
sunset and latest sunrise (from Les, and of course it was correct). So I 
guess everyone else either (1) doesn't know, (2) knows but really doesn't 
care, or (3) simply couldn't care less. I tend to think the latter, based on 
my track record with such minutia!  :o)

Anyway, think of the analemma - that figure eight graph of the Sun's 
declination and the equation of time at equal intervals throughout the year. 
(It often graces the covers of astronomical journals.) The reason that the 
sun moves up and down on that graph is obvious - it changes with the season, 
due to the inclination of Earth's axis. But the left and right motions on the 
graph are due to the Earth's revolution about the Sun. The analemma plots the 
sun's position for local standard time - say noon every day. But Sun time 
(sunrise, transit time, sunset, etc.) varies as the Earth moves about the Sun 
in it's orbit, moving once forward of and then behind local time.

An orrery, or a couple of children's play balls, will serve to show the 
effect of the Earth's orbital motion on sunset and sunrise. Earliest sunset 
occurs at a point just prior to the winter solstice. A little simple 
trigonometry will show that the latest sunset - occurring at the other side 
of the earth, must occur about a month later, as the Earth has moved along in 
its orbit, increasing the angle of your location vis a vis the Sun.

For those who might be interested, perhaps we could get our fearless 
instructor Les to use his marker board to demonstrate the phenomenon some 
night when we're down at FDO or the NC? A flashlight and a soccer ball would 
work, too!

See you all soon,
Doug Stewart
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