The Mark II is a radio telescope located at Jodrell Bank Observatory, near Goostrey, Cheshire, in the north-west of England.

As well as operating as a solo instrument, it has been used as an interferometer with the Lovell Telescope, which provides a 425 m (1,394 ft) baseline.

[3] It is commonly used as part of the Multi-Element Radio Linked Interferometer Network (MERLIN),[4] and for Very Long Baseline Interferometry observations.

The upgrade would have been to a 100 ft circular aperture which could have been used on wavelengths down to 6mm, which would have enabled it to be used as part of the high-frequency component of the original MERLIN array.

[2] The surface was upgraded in 1987 to one with an accuracy of 1/3 mm, which was accurately set using a holographic technique, meaning that the telescope can observe at the 22 GHz MERLIN frequency.

In the late 1990s, a new, more compact carousel for the receivers was installed at the prime focus of the telescope.