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

John R Shakeshaft John is a common English name and surname: * John (given name) * John (surname) John may also refer to: New Testament Works * Gospel of John, a title often shortened to John * First Epistle of John, often shortened to 1 John * Second ...

and colleagues. It comprised a list of 1936 sources between

declination In astronomy, declination (abbreviated dec; symbol ''δ'') is one of the two angles that locate a point on the celestial sphere in the equatorial coordinate system, the other being hour angle. Declination's angle is measured north or south of the ...

s -38 and +83, giving their

right ascension Right ascension (abbreviated RA; symbol ) is the angular distance of a particular point measured eastward along the celestial equator from the Sun at the March equinox to the (hour circle of the) point in question above the earth. When paired w ...

, both in 1950.0 coordinates, and

flux density Flux describes any effect that appears to pass or travel (whether it actually moves or not) through a surface or substance. Flux is a concept in applied mathematics and vector calculus which has many applications to physics. For transport ph ...

. The observations were made with the

Cambridge Interferometer {{Infobox telescope The Cambridge Interferometer was a radio telescope interferometer built by Martin Ryle and Antony Hewish in the early 1950s to the west of Cambridge (between the Grange Road football ground and the current Cavendish Laboratory) ...

, at 81.5 MHz. The data appeared to show a flux/number ('

source counts The source counts distribution of radio-sources from a radio-astronomical survey is the cumulative distribution of the number of sources (''N'') brighter than a given flux density (''S''). As it is usually plotted on a log-log scale its distributio ...

') trend which precluded some cosmological models (such as the

Steady-State In systems theory, a system or a process is in a steady state if the variables (called state variables) which define the behavior of the system or the process are unchanging in time. In continuous time, this means that for those properties ''p'' ...

):- 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 was premature as 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 Telescope The Mills Cross Telescope was a two-dimensional radio telescope built by Bernard Mills in 1954 at the Fleurs field station of the Australian Commonwealth Scientific and Industrial Research Organisation in the area known now as Badgerys Creek, ab ...

in Australia. However, subsequent statistical analysis by

Hewish Hewish is a surname. Notable people with the surname include: * Antony Hewish (1924–2021), English astronomer * James Hewish, Australian short track speed skating referee See also *East Hewish and West Hewish, hamlets in the civil parish of Pu ...

of the interferometer records later showed some aspects of the initial interpretation to have been broadly correct, with the correct measure of the (log(N),log(S)) slope of nearly -1.8 derived once confusion was taken into account. 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.

References

* 2 {{astronomical-catalogue-stub