2C

The Second Cambridge Catalogue of Radio Sources (2C) was published in 1955 by John R Shakeshaft and colleagues. It comprised a list of 1936 sources between declinations -38 and +83, giving their right ascension, declination, both in 1950.0 coordinates, and flux density. The observations were made with the Cambridge Interferometer, at 81.5 MHz.

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The data appeared to show a flux/number ('source counts') trend which precluded some cosmological models (such as the Steady-State):-

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For a uniform distribution of radio sources the slope of the cumulative distribution of log(number, N) versus log (power, S) would have been -1.5, but the Cambridge data apparently implied a (log(N),log(S)) slope of nearly -3.0.

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Unfortunately, this interpretation appears to have been premature - a significant number of the sources listed were later found to be the product of 'confusion', the blending of several weaker sources in the lobes of the interferometer to produce the apparent effect of a single stronger source. (Key data demonstrating this came from the then-recently-commissioned Mills Cross instrument in Australia).

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However, subsequent statistical analysis by Hewish of the interferometer records later showed some aspects of the initial interpretation to have been broadly correct.

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The survey was superseded by the much more reliable 3C and 3CR surveys. The 3C survey also used the Cambridge Interferometer, but at 159 MHz, which helped significantly reduce the 'confusion' (see above) in the later survey.

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Declination: In astronomy, declination (dec) is one of the two coordinates of the equatorial coordinate system, the other being either right ascension or hour angle. Dec is comparable to latitude, projected unto the celestial sphere, and is measured in degrees north of the celestial equator. Therefore, points no...

Right ascension: Right ascension (RA; symbol α: Greek letter alpha) is the astronomical term for one of the two coordinates of a point on the celestial sphere when using the equatorial coordinate system. The other coordinate is the declination. RA is comparable to longitude, measured from a zero point known as...

Flux density: redirect Flux...