A method of measuring the solar rotation

We propose a method to determine the surface velocity of solar rotation. The method rests on measurement of the line-of-sight velocity difference between two elements on the solar disk which are symmetric about the central meridian at the same heliolatitude. This is a simple method which is largely free from the influence of spectrograph noise and instrumental drifts and permits several measurements to be made during one day. Results of trial observations are reported. The rotation curve we have obtained is notable for the large value of equatorial velocity as well as a steeper dip with increasing latitude.