The relationships between these units depend on the fact that there is a simple linear relationship between a tiny parallax angle, in ANY units, and the tangent of that angle.Īctually, 1838 isn't all that long ago. Why am I belaboring this point? Because astronomers have chosen a set of units for parallax calculations which look strange, but turn out to simplify the actual work. Take a look for yourself: Table 2 angle (degrees)
\tan(\pi)\]Īnd, in general, there is a linear relationship between the tiny angle π and its tangent, regardless of the units.