[js1138]

But do parallax measurments work beyond 6000 light years, or far enough to pose a problem to YEC?

[ThinkPlease]

Parallax is used as the first step of the distance scale. It can be used with methods that overlap it to verify distances and extend those methods farther and farther away from Earth. I believe Parallaxes with Hipparcos are good to about 1000 ly, maybe a bit less than that, I forget.

[Right Wing Professor]

Trigonometric parallax is good out to 500 parsecs, or about 1600 light years. However, that's far enough out to calibrate the Cepheid variable scale. (Cepheid variables are a class of yellow variable stars with a fixed relationship between absolute luminosity and period of variation). If you know the absolute luminosity of a star, and its apparent luminosity, you can calculate its distance. And since they've identified Cepheids in the Magellanic clouds (hundreds of thousands of light years away) and in nearby galaxies (millions of light years away), that nails YEC pretty nicely, for about the 150th time.