# What is the parallax formula for astronomy? What is the unit of measurement for the formula?

Parallax is the apparent angular displacement of a space body due to displacement of the position of the observer. As of now, the unit for this angular measure could be $\frac{1}{1000} \sec$..
The unit for parallax depends on the precision of the device used for the measurement. The smallness varies. Currently, the accuracy level is up to 0.001 sec = ${0.00000028}^{o}$.