12.2.2. Parkes Survey
The most extensive survey of the Southern Hemisphere radio sources has
been made with the 210-foot radio-telescope near Parkes,
Australia. This survey was initially made at
408 MHz (75 cm), except for the region
20° > <
27°, which was surveyed at 635 MHz (50 cm). Each source detected in
the 50- or 75-cm finding survey was re-observed
at 20 and 11 cm to obtain more accurate
positions and flux densities at these wavelengths. The Parkes survey
essentially replaces an earlier survey made at 86 MHz using
a Mills Cross-type antenna with a resolution
of about 48 minutes of are. Unlike the Cambridge 2C survey, made about
the same time and at nearly the same wavelength, the Mills
Cross survey was mostly limited - not by
inadequate resolution to separate nearby
sources, but by low sensitivity. Nevertheless,
later work has shown that this survey was
surprisingly accurate for its time, at least for
the sources not near the limit of detection.