This 2.44m (8ft) achromatic zenith sector telescope was commissioned by the Astronomer Royal John Pond and built by P. & J. Dollond in 1816. It was built to work to replace the zenith tube AST0994 which had a fault preventing it ever working successfully. No records of observations have been found from this instrument so how it was used it unclear. Though it continued to be mounted in the circle room until 1846 its working life ended in 1822 when it was realised the same measurements could be made and more accurately with the mural circle alone.

A zenith sector is a telescope that points straight up, to the zenith. This means that it can only see the stars directly above and are usually designed with the observation of a particular star in mind. This telescope for example was designed to allow observers to study the position of the star Gamma Draconis (the third brightest star in the constellation Draco) very accurately over the course of the year. A major reason for doing this is to allow astronomers to account for the error introduced by atmospheric refraction. At any angle besides straight up the atmosphere with refract the light coming in from a far away star making it appear in a slightly different location to its actual position. The amount the atmosphere refracts the light will vary depending on the weather. If observations are compared with those made with the zenith sector however, this error can be accounted for.

Telescope: This telescope has an achromatic object glass made by Peter Dollond with an aperture of 70mm (2.75inches) and a focal length of 2388mm (7ft 10 inches). The object glass was reused from a previous telescope, the 8ft transit instrument (AST0980).

Mount: Mounted onto the back of the circle pier (replacing AST0994).

Accessories: eyepieces and micrometers for this instrument are missing.