I have this formula to calculate the refraction of a star in the sky (the difference between where the star appears and where it really is.)
$z_0 = z + 60''\times \tan z$
where $z_0$ is the fraction and $z $ the zenith distance in degrees.
My question is if I multiply 60 angle-seconds times the tangent of $z$, which unit does this have? $\tan z$ is the ascending of the angle but I´m having trouble knowing which unit the result have.