J2000.0 clarification

[Whoosh900]

Hi

I am trying to understand J2000.0 and the geocentric equatorial celestial coordinate system.

Am I correct in saying:

The reference plane is defined by the 3 points:

1) center of mass of sun @ J2000.0 (not the Solar System Barycenter (SSB))

2) center of mass of earth @ J2000.0

3) center of mass of earth @ Equinox 20 March 2000 07:35 UTC "Vernal Point"

The Equator used to determine the Vernal Point is the "mean equator"

The origin of the frame is the center of mass of earth @ J2000.0.

RA = 0 is defined by the Vernal Point.

The error introduced by the orbit of the earth around the sun is ignorable for deep sky objects?

In other words I could consider the origin to be anywhere inside the earth's orbit and the coordinates will be acceptable ...

Where can I find a definitive explanation?

[Whoosh900]

all this is deprecated now, as explained by this PDF:

http://syrte.obspm.fr/iau/iauWGnfa/wallace_com8_ga06.pdf

the reason I could find no answer - is because there is no answer