Dolphin equinoctial dial for latitude 51° 28' North. The dial sits on an octagonal plinth made of Portland stone. A cresting wave is set on the plinth and supports the curved dial-plate, which forms part of a cylinder and is inclined so that it lies in the plane of the Equator. Two bronze dolphins hold the dial-plate in their mouths and curve over so that their tails almost meet above the dial-plate. The centre of the gap between the two tails acts as the gnomon.

There are two dial-plates and two rims: the rims are set for Greenwich Mean Time and British Summer Time. Each rim is engraved with the names of the makers and the words 'FOR NOW IS ALL THE TIME THERE MAY BE'.

The dolphin dial was designed in 1977 by Christopher Daniel, Head of Education Services at the NMM, to mark the occasion of Queen Elizabeth II's Silver Jubilee. The sculpture was made by Edwin Russell and the object was cast at Brookbrae in London. The dial was unveiled on 5 June 1978 at 1 pm (midday, Greenwich Mean Time) in a specially designed paved setting in the Museum's south grounds. In 2009, after removal as part of preparatory work for the Sammy Ofer Wing, it was resited as centrepiece of the redesigned Astronomer's Garden at the Royal Observatory . The use of the different dial rims for Greenwich Mean Time and British Summer Time and of the two different hour-plates with the hour-lines marked as half of the analemma, means that the instrument is always accurate to the nearest minute. The rims are changed when the clocks change for daylight saving at the end of March and October while the hour-plates are changed at the solstices in June and December.

For more information regarding this dial please refer to the OUP & NMM catalogue, 'Sundials at Greenwich', pp.158-159.