The Second Cambridge Catalogue of Radio Sources (2C) was published in 1955 by J 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.

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

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.

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).

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

The survey was superceded by the much more reliable 3C and 3CR surveys.

Reference

Shakeshaft J R, Ryle M, Baldwin J E, Elsmore B & Thomson J H (1955) Mem RAS vol 67, pp106-154