The radio telescope at the Algonquin Radio Observatory, located in Algonquin Park, Ontario, is typical of the radio telescopes built around the world in the 1960s.

It is a spectacular instrument with a 46-metre dish. At an operating wavelength of 2.8 centimetres it can "see" a patch of sky about one tenth the diameter of the Moon in the sky.

That means that pointing the instrument at known cosmic sources of radio waves and measuring the strength and other properties of their radio emissions is quite easy. However, using it to map a large area of sky involves scanning the region of interest, measuring the radio brightness one "pixel" at a time.

Searching the sky for unknown, new objects would also be a very tedious process. The operating cost of large telescopes like that one does not encourage large-field mapping projects because of the time involved and largely rules out more speculative searches, making purely serendipitous discoveries rare.

There is always........

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