[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.

[RadioAstronomer]

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.

Don't forget SN1987a. :-)