The Culgoora magnetograph.
A magnetograph has been developed with the intention of producing magnetograms of spatial resolution approaching or surpassing 1 arc s with a fast repetition rate. The spatial resolution achieved at present is about 2 arc s, and observations may be obtained over a circular field of one-quarter the solar diameter every 8 s. The instrument consists of a telescope with which filtergrams are obtained simultaneously in opposite circular polarizations in the wing of a magnetically sensitive line, and a subtractor which displays the image differences due to the longitudinal magnetic field.
Ramsay, J. V.↗