John, About the projection sundials you may read at my homepage. Address below. Use the link Projection dials.
It is an article by J.A.F. de Rijk, Netherlands, also published in 1986, 97, 1 Journal British astronomical Association. Equator projection sundials Best wishes, Fer. Fer J. de Vries [EMAIL PROTECTED] http://www.iae.nl/users/ferdv/ Eindhoven, Netherlands lat. 51:30 N long. 5:30 E ----- Original Message ----- From: <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]>; <sundial@rrz.uni-koeln.de> Sent: Thursday, October 04, 2001 8:48 PM Subject: Re: Projection Sundials > 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 >
