Parallax Equations

[Brady Yoon]

While reading my introductory astronomy textbook, I read about two formulae that were used to determine distances using parallax.

One was d(parsecs)=1/p(parallax in arc seconds), but I vaguely remember something like:

distance=baseline*(parallax in degrees/57.3)

What is this second formula and when is it used/is it the same as the 1st, but written in a different form?

Thanks!

[tony873004]

The Parsec is a unit invented just for parallax.

Theta = a/d

a is in AU. d is the distance in parsecs. Theta is in arcseconds.

Theta = a/d also works if a and d are in the same units. But then Theta is in radians.

[Ken G]

distance=baseline*(parallax in degrees/57.3)

What is this second formula and when is it used/is it the same as the 1st, but written in a different form?

Note this second formula must be wrong, as it has parallax increasing with distance, which of course can't be right. Stick to tony87304's forms.