The Altazimuth Pavilion is topped with an unusual weather vane.

It is modelled on Halley’s Comet, as depicted in the Bayeux Tapestry. It was erected in June 1901, a few years after the building was completed but in time for the comet’s return in 1909. There is a clear link with the Observatory’s history since Halley was the second Astronomer Royal, although his famous prediction was made fifteen years before he took up the post. It is not clear why the illustration from the Bayeux Tapestry was used as inspiration, although its shape is ideal for catching the wind and echoes that of the weathervanes of the Royal Naval College down the hill.