The brightness distribution of 21-cm radiation over the Sun's surface has been studied for the past four years with the Christiansen crossed-grating interferometer (Christiansen et al. 1961) at Fleurs near Sydney. The observations described here were made using one arm of this cross as a simple grating interferometer, providing a transit instrument with a fan beam of about 2' of arc resolution to half-power points in the east-west direction and very low resolution north-south. The Sun was scanned repeatedly from east to west at time intervals of approximately 4 min.
Solar radio burst and in situ determination of interplanetary electron density