Heston Community Garden Sundial

Location:     Heston Community Garden, Sutton Playing Fields, The Crossways, Heston, Hounslow TW5 0JG

This is a ceramic dial formed from a wheel-thrown pot which provides the requirements for an equatorial sundial with a calendar, Equation of Time, and several features contributing to a global awareness and connection to the cosmos.

How it works

The gnomon is thrown with the pot, as a conical form at the centre, naturally concentric with the internal spherical surface on which its shadow is projected.  The shadow is thus a consistent symmetrical shape of which it is easy to judge the centre‑line which indicates the time of day.  Both GMT and BST hours are shown, at the top and bottom of the scale respectively, as appropriate to the general location of the shadow in Winter and Summer.  The height of the shadow indicates the time of year on a vertical scale delineated in months.  The Equation of Time analemma is shown at the 12.00 o'clock line.  The initial letters identifying months are positioned next to the relevant section of the analemma to enable a visual conversion of sun time to clock time.

How it's made

Before firing, when the clay is 'leather hard', the pot is tilted and sliced at the intended angle of latitude so that the rim becomes the horizon, and the gnomon can point in the polar direction.  Using some relatively simple jigs, all the markings on the dial are scribed into the clay and filled with manganese dioxide.  In the subsequent firing (to 1200°C) the oxide converts to a dark brown impervious glaze.  The sliced off piece of clay is used to make the foot of the sundial.  The plinth is an antique ceramic chimney pot, in harmony with the ceramic dial.

How to use

Instructions will shortly be on the Community Garden website (https://www.hestonactiongroup.co.uk/) , later to be accessed by a QR code label on the plinth.