Year 2004

Work of our members

Sundial with constellations.

The artist designed the horizontal sundial presented here for the town of Zoetermeer, provence South Holland.
A design sketch, with better detail, is on the bottom of this page.

The sundial shows the constellations as they appear on 28 Augusts, 24:00 local apparent time, because that is the recipient’s birthday.

The individual stars making up the constellations were gnomonically projected onto the dial face; that is by projecting the sky, along the direction of the stylus, onto the dial face.
Also shown are some signs of the Zodiac (Aries, Pisces, Aquarius, Capricorn), and the ecliptic.

The date lines for the start of the seasons are also on the sundial. Interestingly, these may be regarded as projections of the declination circles of 0 degrees – the celestial equator – and of 23.5 and -23.5 degrees – the tropics.

The shadow caster has a brass index. At the start of every season, the shadow of this index moves along the corresponding date line.

When the index shadow crosses the ecliptic, this indicates the position of the sun among the stars.
The dial shows, for example, that the celestial equator neatly intersects the ecliptic in the first of Aries, which is the position of the sun on 20 March.

The edge of the sundial shows the zodiacal signs. Between these signs, the difference between local apparent time (which the sundial shows) and civil time is noted.
Cancer, for example, runs from approximately 21 June up to 21 July. The sundial shows that around 21 June, 44 minutes should be added to the dial time in order to arrive at civil time. On 21 July, this would be 48 minutes.

The sundial is made of granite, 50 cm (20 in) square, 3 cm (1 3/16 in) thick.
The artwork is dye-filled intaglio. The gnomon is made of 4 mm (5/32 in) thick brass.