Portable transit telescope

Telescope and stand for Reversible Transit Circle. From a transit of Venus expedition of 1874, it is labelled 'Transit D'. This refers to the location it was sent to, Station D was Christchurch New Zealand.

Both this, the transit intrument 'B' sent to Honolulu and transit instrument 'C' sent to Rodriguez Island were later used for time-determination at the Royal Observatory, Greenwich and then at its outpost at Abinger between 1927-1957. In 1967 'C' [AST0986] was presented to the NMM. Transit instrument 'A' [AST0988], which had been sent to Egypt and then to the Royal Observatory at the Cape returned to Greenwich in 1977. This transit instrument 'D' remained with the Royal Greenwich astronomers until the closure of the RGO in 1998 when it returned to the original Greenwich site.

This telescope was altered sometime after the transit of venus expedition, alterations include an electric attachment for getting uniform illumination across the cross-wires on the eyepiece.

Telescope: 3 inch aperture telescope with a 36.5 inch focal length.

Stand: The original stands for each of the 5 transit of Venus transit instruments had been stone piers, 4ft 11 inches high, each weighing 1400lb. These were replaced by in 1892 with the cast-iron stands we have now each fitted with apparatus for rapidly reversing the telescope.

Box and accessories: would originally have fitted into two travelling cases. These are now missing.

Object Details

ID: ZBA1731
Collection: Astronomical and navigational instruments
Type: Telescope
Display location: Not on display
Creator: Troughton & Simms
Places: Christchurch
Events: Transit of Venus, 1874
Date made: circa 1870
Credit: National Maritime Museum, Greenwich, London
Parts: Portable transit telescope

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