The Discovery of Quasars and its Aftermath
  Although the extragalactic nature of quasars was discussed as early as 1960,
it was rejected largely because of preconceived ideas about what appeared to be
an unrealistically high radio and optical luminosity. Following the 1962
occultations of the strong radio source 3C 273 at Parkes, and the subsequent
identification with an apparent stellar object, Maarten Schmidt recognized that
the relatively simple hydrogen line Balmer series spectrum implied a redshift
of 0.16 Successive radio and optical measurements quickly led to the
identification of other quasars with increasingly large redshifts and the
general, although for some decades not universal, acceptance of quasars as
being by far the most distant and the most luminous objects in the Universe.
Curiously, 3C 273, which is one of the strongest extragalactic sources in the
sky, was first cataloged in 1959 and the magnitude 13 optical counterpart was
observed at least as early as 1887. Since 1960, much fainter optical
counterparts were being routinely identified using accurate radio
interferometer positions, measured primarily at the Caltech Owens Valley Radio
Observatory. However, 3C 273 eluded identification until the series of lunar
occultation observations led by Cyril Hazard, although inexplicably there was
an earlier mis-identification with a faint galaxy located about an arc minute
away from the true position. Ironically, due to calculation error, the
occultation position used by Schmidt to determine the redshift of 3C 273 was in
error by 14 arcseconds, and a good occultation position was not derived until
after Schmidt had obtained his 200 inch spectrum.
