Re: Summer Solstice Calculation Questions


Sam Wormley wrote:
S. Caro wrote:
Sam Wormley wrote:



Good thing I looked this up, as I would have been totally wrong!

Explanatory Supplement - Astronomical Almanac

9.211 Equinoxes and Solstices (pg 477)

The times of the equinoxes and solstices are *defined* when the Sun's
*apparent ecliptic longitude* lambda_s is a multiple of 90°; i.e.,
it is calculated from f(t) = 0, where f(t) = lambda_s -0°, 90°, 180°,
or 270°. Thus in the northern hemisphere, for the spring equinox
f(t) = lambda_s, for the summer solstice, f(t) = lambda_s - 90°, for
the autumn equinox f(t) = lambda_s - 180° and for the winter solstice
f(t) = lambda_s - 270°. At the equinoxes the Sun crosses the equator
when the length of the day exceeds the length of the night due to
refraction, semidiameter, and parallax of the Sun. At that time the
lengths of the day and night are approximately equal everywhere.


Does the analemma effect not factor into this ? (Perhaps the math
above explains it :-)



The analema is a figure 8-shaped plot of the apparent Sun relative to
the mean Sun. This curve is sometimes seen on globes, maps and the
photography of Dennis di Cicco and most notably, Anthony Ayiomamitis!
And it does change slightly over the millennia.


The analemma is a consequence of using a human devised principle that
is the equable 24 hour day to register the Sun against the
Equator/axis,it is so childish that it can only mean the noble
discipline of astronomy has reached a dire state.

Natural noon sunlight strikes the sundial on the exact same line
throughout the year,the shadow may be long or short depending on the
orbital orientation of the Earth at specific points in its annual
orbit but there is no figure 8..

The reason that the determination of natural noon is vital using the
line on a sundial is that the Equation of Time correction is applied to
the natural noon event to reduce the total length of the natural
unequal day to the equable 24 hour day.

Those horrible creeps in the 17th century,in attempting to use the
celestial sphere to gauge terrestial longitudes forced an axial tilt
component to the Sun and kept the Earth orientated to a celestial
sphere.A 21st century person would marvel at the audacious vandalism
wrought on the Equation of Time correction and move on but the utter
incapacity of men to be clinical is removing the hideous corruption
only highlights the dominance of the destructive empirical cult.

How I enjoy turning a scrap of astronomical information into something
entirely different while you plod along with dull and dreary comments
based on a celestial sphere.

.

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