Authors: Roger K. Ulrich (University of California at Los Angeles)

The magnetograph developed by Babcock(1953), \citet{1955ApJ…121..349B}, and \citet{1960ApJ…132..218H} has been used by research groups supervised by Robert Howard, Gary Chapman and Roger Ulrich. Improvements in the calibration and analysis methods by \citet{1983SoPh…87..195H} resulted in a significant reduction in the scatter of the determined rotation rates that the results reported here begin the first of the year 1983. A program of multiple observations per day begins in 1985 which further reduces the variation in averages over multiple Carrington rotations. Observations ended at the beginning of 2013 due to equipment failure and the ending of funding. Continued analysis of the 1983 to 2013 observations has resulted in improvements to the reductions which show new features in the differential rotation rate variations and in the determined meridional circulation patterns. These are shown in the figures above.

Babcock, H. W.: 1953, The Solar Magnetograph. Astrophys. J. 118, 387