Hi David, The reason that the term "projection sundial" doesn't appear in the BSS Glossary is that it isn't, as far as I'm aware, a term used in the general literature.
The dials listed under the term in Sundials Australia are a strange collection of dials usually defined under other tems. There is a ceiling (or reflection) dial, an analemmic dial, a noon dial, a sun compass etc etc. It is difficult to see what they have in common. It would be possible to make a definition for a projection dial based on the principle of projecting a spot of light onto a receiving surface, but that is just about as general as dials which make shadows on surfaces. However, there are a lot of terms already so I'm not in favour of inventing new ones unnecessarily. But I'm prepared to be overruled! John Davis (Glossary Editor) > Dear All, > > Could someone help me with a definition of a 'Projection Sundial'. > > - Couldn't find it in the BSS Glossary. > > - Folkard & Ward 1996 "Sundials Australia" have included in their section on > Projection Sundials - The chapel sundial (Merton College, Oxford), a Sun > Compass, a direct sunlight through a hole onto analemmas on the horizontal > ground, Monash University Union Building- Melbourne Australia (wall mounted > rod tipped by a disk making shadows on analemmas on a wall), the Augustus > Sundial from 9BC, Ulugh Bek's Observatory, mirror sundials shining on > analemmas on a roof, various noon marks and a Scottish polyhedral 'lectern' > sundial. > > The common factor seems to be that the shadow (or light ray) approximates a > point rather than a segment. > > Is Projection Sundial a recognised term? > > What is the characteristic that Projection Sundials have that other sundials > don't? > > > David Pratten > www.sunlitdesign.com
