[VadeRetro]

The farthest man can accurately measure from earth is about 20 light years some will say 100, this is all due to the angle the earth makes in the rotation around the sun which would be about 1 degree when measured 6 months apart, in those kind of distances it would be like looking down a straight line, it would not even resemble a triangle.

Have you been reading some old science books? Say, 200 years old?

[longshadow]

re: Limits of parallax techniques.

Hipparcos's original design goal was parallaxes with a standard deviation of 2 to 5 milliarcseconds, depending on brightness and position on the sky.

If you want the relative error of the observed parallax (i.e. the ratio observational error / observed parallax ) to be (say) 10%, then that means (taking the 2 milliarcsecond figure for purposes of discussion) Hipparcos parallaxes are good down to 20 milliarcseconds, i.e. out to 50 parsecs (= 165 light years) distance. On the other hand, if you can live with 20% relative errors, then the parallaxes are good down to 10 milliarcseconds, i.e. 100 parsecs (= 325 light years) distance. Or if you need 1% relative errors, then they're only good down to 200 milliarcseconds, i.e. out to 5 parsecs (= 16 light years) distance. Etc etc.

source: http://www.cv.nrao.edu/fits/traffic/sciastroresearch/sar.9707

FWIW, Hipparcos was originally intended to do parallax distance out to somewhere in the 800-1000 ly range, but it got stuck in a smaller parking orbit, thus reducing its range.

[Creationist]

Do you know how to use trig?