RE: Projection Sundials

[david]

Dear Fer,   The BSS glossary does contain this entry:   equatorial projection ~: a class of dials obtained by projecting a universal equatorial ring dial onto any plane. Members of the class include analemmatic, diametral, Foster-Lambert and Parent dials. Which covers the usage that you are referring to.  Didn't find the entry earlier.  In anycase, it would seem that I have misnamed this sundial.    Suggestions for a more appropriate name?  Perhaps "Equatorial Analemmic"  would be more appropriate?    ("Double Barrelled Overhead Gnomon Oblique Cylinder" does not need to be suggested.)   One interesting feature of this sundial design is that (mean time) of the solar transit and sunrise/sunset times may be read off the dial face for the whole year.  With appropriate markings, the azimuth of sunrise/sunset could also be read off.   While I 'discovered' this sundial design independently, I suspect that it has a history.  Can anyone point to earlier presentations of this design?     Thanks   David    -----Original Message----- From: fer j. de vries [mailto:[EMAIL PROTECTED] Sent: Friday, 5 October 2001 1:10 AM To: [EMAIL PROTECTED]; Sundial Subject: Re: Projection Sundials Hello David,   The term Projection Sundial also is used by J.A.F. de Rijk, Netherlands, in an article (1986, 97, 1 Journal British astronomical Association. Equator projection sundials) that is also pubished on my Website. Use the link Projection dials from my homepage. Address below.   As such it is the projection of a universal equatorial ring sundial onto any plane and into any direction. You then get all kind of analemmatic and Foster's 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: Sundial Sent: Thursday, October 04, 2001 5:38 PM Subject: Projection Sundials 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