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2nd of December 2022
The Potts Hill confirmation of the 21cm line
Yesterday's ADAP described an antenna on a lake -- today's image is of an antenna that was located by the Potts Hill reservoirs in western Sydney (and that was recently featured on the CSIRO_ATNF twitter feed). In 1948, this 4.9m x 5.5m (16-ft x 18-ft) ex-radar paraboloid, that had originally been used for solar work at the short-lived Georges Heights field station, was relocated to Potts Hill. The original crude support was replaced by an equatorial mounting, and this radio telescope was one of the principle instruments at Potts Hills in the early days, operating at 200, 600 and 1200 MHz. Following a cable to Pawsey in March 1951 from Frank Kerr, then visiting the USA, Christiansen and Hindman embarked on a crash program to confirm the detection of the 21-cm neutral hydrogen line made by Ewen and Purcell. Within several weeks they had built a narrow-band receiver for the telescope and made the first hydrogen line observations of the southern sky. More details are given in this paper by Rod Davies and this ATNF News article by Wendt, Orchiston, and Slee.

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