Friday, 23 January 2009

28-inch telescope

B5698 28-inch telescope at Royal Observatory Greenwich, c. 1894 © NMM

This image shows the 28-inch refracting telescope at the Royal Observatory in Greenwich in about 1894. The Assistant in charge of the Photographic and Spectroscopic Department, E. Walter Maunder, is at eyepiece of the half-spectroscope (designed by the Astronomer Royal, William Christie) and W. Bowyer is taking notes.

This telescope, with its large 28-inch aperture, is still the largest in Britain and the seventh largest telescope in the world. It is described in detail on the National Maritime Museum's website and the telescope itself can still be seen and used at the Royal Observatory Greenwich. It was built by Sir Howard Grubb of Dublin and mounted in 1893 on the same mount as that designed for the Great Equatorial telescope. It was designed with an objective glass that could in part be reversed in order to correct the focus for use with photography. In practice this was little done after Christie's 1894 trials and the telescope was mainly used for double-star observations. From the 1950s to 1971 the 28-inch was transferred to the Royal Greenwich Observatory's new home in Herstmonceux, Sussex. After the original Greenwich site became a museum the telescope was returned and put on public display.

D0887_2 The 28-inch telescope at the Royal Observatory Greenwich © NMM

Because the 28-inch was a larger telescope than the Great Equatorial in order for the same mount and building to be reused it was necessary to replace the dome. Originally drum-shaped, the now familiar onion-dome became a feature of the Greenwich skyline in 1893. This was badly damaged in the Second World War and the current dome is a modern replacement. See the 28-inch's photo history at the NMM website.

Rebekah Higgitt

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