Here's a good discussion of parallax:
http://web.archive.org/web/20100826022827/http://www.realityreviewed.com/Negative%20parallax.htmwritten by:
Dr. Neville Thomas Jones, Ph.D., D.I.C., M.Sc.(Phys), M.Sc.(Comp), B.Sc.(Hons),
formerly of the Clarendon Laboratory, Oxford University, England.
Roughly 46% of stars have no parallax, 29% have parallax, and 25% have negative parallax. Negative parallax is a problem for the a-centrists (as he calls them), so they conveniently just discard these as "errors".
The phenomenon of stellar parallax is not what we have been generally led to believe, because in exactly the same way that Eddington 'proved' Einstein's General Theory of Relativity in 1919 by rejecting, omitting or deleting 60% of his measurement data on the bending of starlight, so modern astrophysics maintains the misconception that parallax 'proves' the Kopernikan philosophy of the World hurtling around the Sun, by ignoring and dismissing the entire dataset of negative parallax measurements.
I've also never really seen it taken into account that in a period of a year, modern sciences claims that the earth would move about 11.5 BILLION miles through through the universe.