Flandrau Heliochronometer Photos on Registry

[John Carmichael]

Hello all,
 
With Robert Terwilliger's and Robert Kellog's 
patient help, I've updated all known sundials in Arizona on the NASS registry. 
Included are several fine photos and a lengthly description of my Flandrau 
Planetarium Heliochronometer.
 
Go to: http://www.sundials.org/registry/
and click on "Arizona".  Scroll down to Tucson 
and look for sundial # 464.
 
John
 
John L. Carmichael Jr.Sundial Sculptures925 
E. Foothills Dr.Tucson Arizona 85718USA
 
Tel: 520-696-1709Email: [EMAIL PROTECTED]Website: 

Projection Sundials

[david]

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 

Re: Projection Sundials

[john . davis]

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