Mark II

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This article is about the radio telescope. There is also a US-made World War II hand grenade called "Mk 2 grenade"

Mark II
The Mark II
Organization:	Jodrell Bank Observatory, University of Manchester
Location:	Cheshire, United Kingdom
Built:	1964, upgraded 1987
Diameter:	38.1 m, 25.4 m
Focal length:	12.2 m
Mounting:	Alt-Azimuth

The Mark II is a radio telescope located at Jodrell Bank Observatory, near Goostrey, Cheshire, in the north-west of England. It was built on the site of the old 218 ft (66.4 m) Transit Telescope. Construction was completed in 1964.

The original dish surface of the telescope was more accurate than the Lovell Telescope's at the time it was made, meaning that it was better suited for observations at higher frequencies. As well as operating as a solo instrument, it has been used as an interferometer with the Lovell Telescope, which provides a 425m baseline. It is commonly used as part of the Multi-Element Radio Linked Interferometer Network (MERLIN), and for Very Long Baseline Interferometry observations.

[edit] Technical specifications

It was designed by Charles Husband at the instigation of Bernard Lovell, and was originally intended as a prototype for a larger, "Mark IV" telescope, which was never constructed. The design is very similar to the Goonhilly 1 telescope. The Mark III telescope is also based on a similar design.

It has an elliptical dish, with a major axis of 125 ft (38.1 m) and a minor axis of 83 ft 4 in (25.4 m). The focal length is 40 ft (12.2 m). The original surface had an accuracy of ±1/8 inch; it was upgraded in 1987 to one with an accuracy of 1/3 mm, which means that the telescope can observe at the 22 GHz MERLIN frequency. The new surface is circular and was laid on top of the old, such that the telescope now has ear-like extensions where the old surface still shows.

It has an alt-azimuth mount sitting on 54 steel rollers in a 42 ft (12.8 m) diameter roller track on top of a foundation block. It was the first telescope in the world to be steered by a digital computer. This computer, the Ferranti Argus 104, had 12 kilobytes of memory; it was upgraded to an Argus 400 in 1971.

A proposal to upgrade the Mark II to a Mark IIA was put forward in 1974. The upgrade would have been to a 100ft circular aperture which could have been used on wavelengths down to 6mm. However, the upgrade was never approved.