The Earth's rotational axis points towards the North Celestial Pole,
90°N (indepensent of Right Ascension, althought there might be a
conventional RA used when describing the pole that I'm unaware of).

The Earth's axis of revolution (around the Sun) points towards the
North Ecliptic Pole, at 18h 00m 00s +66° 33' 39" (epocj 2000).
So, "d".

This is in constant change, and the Earth's rotational axis traces out
a cone whose axis aligns along the line towards the NEP over the
course of about 26kyrs.

Some easily observed characteristics are the change of seasons, and
the cycle of the Sun appearing to rise and set at different places
along the east and west horizons, respectively, over the course of a
year.

??

On 19 Mar 2006 15:19:04 -0800, "canopus56"
wrote:

Tomorrow is the spring equinox. This got me to thinking about
orientatoin of the Earth's axis with respect to its direction of travel
in its orbit around the Sun. Although the Earth's axis is tilted at 23
1/2 degrees in the ecliptic z-plane, what is the axis's orientation
with respect to the ecliptic x-y plane? Does it point:

a) in the direction of Earth's direction of revolution;
b) perpendicular to Earth's direction of revolution;
c) opposite Earth's direction of revolution; or,
d) some other angle?

I assume this changes over geologic time as the Earth wobble's around
it's center on a 28,000 year cycle.

What easily observed characteristics of the solar daily or yearly cycle
would indicate the direction of the tilt in the x-y ecliptic plane?

- Canopus56

=============
- Dale Gombert (SkySea at aol.com)
122.38W, 47.58N, W. Seattle, WA
http://flavorj.com/~skysea