You are aware, are you not, that astronomers use an inertial reference
frame based on the optical and radio postions of distance quasars, to
prevent just such errors?


There is no constant displacement of .986 degrees for the orbital
motion of the Earth but this is what is used to justify the sidereal
value and axial rotation.

You are aware, are you not, that your reply has nothing to do with my
question? How about you answer my question?

And no one claims there is a "constant" displacement. There is an
average displacement though.