On Apr 26, 12:04*pm, "Mike Dworetsky"
wrote:
"Les Desser" wrote in message

...





I am preparing a presentation on the Equation of Time and have been trying
to find a clear description, preferable with diagrams, of the adjustment
due to obliquity.

The explanation at the National Maritime Museum
http://www.nmm.ac.uk/server/show/conWebDoc.351 only makes sense if you
already know the answer

The best I could find was the page at
http://www.wallingfordclock.talktalk.net/Sidereal%20Time.htm but I still
find it inadequate.

The example of the bus going down the incline is good to show the slowdown
but I cannot find anything appropriate to explain the speeding up.

Has anyone seen and better presented explanations?
--
Les Desser
(The Reply-to address IS valid)

I recommend the following web site:

http://www.analemma.com/

There is a diagram, possibly what you are looking for, that separates the
obliquity and eccentricity effects, at the Royal Observatory web site:

http://www.nmm.ac.uk/server/show/conWebDoc.351

Try also wikipedia on both topics.

--
Mike Dworetsky

(Remove pants sp*mbl*ck to reply)- Hide quoted text -

- Show quoted text -

By all means keep the NMM explanation and especially this gem-

'The equation of time due to obliquity (the Earth's tilt) '

"The angle between the planes of the equator and the Earth's orbit
around the Sun is called the angle of obliquity.
If the Earth's rotation axis was not tilted with respect to its orbit,
the apparent motion of the Sun along the the Ecliptic would fall
exactly on the equator, covering equal angles along the equator in
equal time. "

http://www.nmm.ac.uk/server/show/conWebDoc.351

It would be really nicve to have adults who can openly discuss how
variations in daylight darkness North and South of the Equator and
variations in the natural noon cycles everywhere have the same
astronomical root based on the relationship between axial and orbital
motions.The reasoning of the NMM where rotational orientation has some
effect on Kepler's orbital geometry and the variable noon cycles
is ,to put it mildly,as childish as it gets.

The shared mechanism which causes no variations in daylight/darkness
at the Equator yet variations in the natural noon cycle there requires
the addition of an orbital component,one that is already observed by
looking at the orbital behavior of Uranus.

Just to remind you Mike,in the Piltdown Man episode,it was not the
people who were taken in by the hoax or those who built on the ideas
that became the most hated and despised ,it was those who knew it was
a hoax and kept it going out of personal convenience. even though it
had no productive legs.I am willing to concede that it is difficult to
extract the orbital component as a seperate motion with respect to the
central Sun whereas axial rotation occurs simultaneously as a seperate
motion thereby thew whole scheme becomes a modification of
heliocentric reasoning.The hoax comes in via the analemma where
variable inclination to the Sun was introduced despite the fact that
rotational orientation as a consequence of axial rotation keeps the
Earth pointing towards pOlaris throughout an annual orbit.

I do not know what it takes to shatter this sidereal monster and its
destructive effect on the noble Equation of Time scheme but it
requires genuine people who do not repeat old falsehoods as you have
just done.