HI all
Thanks to all who replied to my question regarding the equation
of time correction. Sorry for the late reply but my E-mail has not been
working after upgrading my system to a Pentium 100.
My question was:
>
> My question is with regard to the tilt of the earth axis effect.
>
> The SUNDIAL AUSTRALIA ISBN 0 646 22200 7 book indicates that (for the
> tilt of the earth axis effect) there is no difference between local
noon
> and solar noon at dates corresponding to the Equinoxes and Solstices
(4
> times per year), but produces a difference of up to +/- 9.86 minutes
> between each Equinox and Solstice (4 times per year).
>
> Can someone please explain and describe the above effect.
>
> Thanks in advance: Roderick Wall
>
>-- End of excerpt from Roderick Wall
All the replies that I have received has helped me a little, but I am
still having problems understanding the earth axis effect.
In the British Sundial Society BULLETIN No. 93.3 October 1993 page
figure 1 it shows A diagram of the Celestial Equator and its
relationship to the Ecliptic.
On page 9 it says: The first problem arises from the fact that time is
measured with respect to the celestial equator. and the motion of the
sun along the ecliptic, when projected in the direction parallel to the
celestial equator, changes throughout the year.
I can see that because the sun is also moving away from the Celestial
Equator ( as well as along it) that for one unit of movement (say 15
deg) then the movement along the celestial equator will be less (less
than 15 deg).
What I don't understand is that: At the summer solstice (and winter
solstice) the motion of the sun is parallel to the Celestial Equator and
I would think that one unit of motion of the sun would equal the same
amount on the Celestial Equator. But Figure 2 (at O) shows that the rate
of change is still high (The point half way between the vernal equinox
and the autumnal equinox). Also if the distance of movement along the
Celestial Equator is less than one unit then at some other time the
movement must be more than one unit to catch up with time.
What am I missing in trying to understand this?
Thanks in advance again. and sorry for the late reply.
Roderick Wall
--
_______________________________
Roderick Wall
E-mail: [EMAIL PROTECTED]
Melbourne Australia.
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