The parallax equation is used to measure the distance to a star by calculating the angle of parallax, which is the apparent shift of the star's position when viewed from different points.
The unit of measurement for distance in the parallax equation is typically kilometers (km) or light years (ly).
To solve the parallax equation, you need to know the baseline distance between the two viewing points, the angle of parallax, and the angle of separation between the two viewing points.
No, the parallax equation can only be used for relatively nearby stars within a few hundred light years. For more distant stars, other methods such as spectroscopy or standard candles are used to determine their distance.
The accuracy of the parallax equation depends on the precision of the measurements of the angles of parallax and separation. With modern technology, the accuracy can be as high as a few milliarcseconds, which corresponds to a distance error of less than 1% for stars within 1000 light years.