Re: Discs + holes, Sundiale near Cph.

[Chris Lusby Taylor]

Hi Thyge,
Thank you for your contribution to this interesting 
debate. Your sundial is stunning. Trust the Danes to show the rest of the world 
how to apply good modern design ideas to old products.
 
Yes, we had realised that a circular disk parallel to the 
wall would cast a circular shadow. The issue was what happens, especially 
to the image of the circular hole in the middle of the disk, when the angle of 
incidence to the wall is very small. Your dial overcomes this, very sensibly, by 
limiting the width of each dial but having one on each face. Thus the sun is 
only on each dial for about 3 hours either side of when it is directly in front 
of the dial. So you never have the problem that John Shepherd 
described.
 
But imagine if your East-facing dial went back much 
further towards the shopping centre. Then, towards noon the shadow would become 
very long and indistinct. Also, the hole in the middle would become 
noticeably elliptical. John's point is that you are then better off with 
two intersecting lines. I'm inclined to agree with him, though I am somewhat 
surprised at the poor shadow he photographed just three hours before noon. In my 
experience a disk is quite usable over a longer time than that. Your photo of 
your east-facing dial on 3rd May at 11:02 shows the disk very clearly, even 
though the sun's azimuth was only 43 degrees east of south.
 
On of my favourite dials is the bifilar, but I had doubted 
whether people would understand and accept reading the intersection of two 
shadows. John encourages me to think they will.
 
Best wishes
Chris
51.4N, 1.3W
 

  - Original Message - 
  From: 
  Thyge Lauritsen 
  To: sundial@uni-koeln.de 
  Sent: Saturday, May 20, 2006 12:05 
  AM
  Subject: Discs + holes, Sundiale near 
  Cph.
  
  
  Dear all members.
  If I 
  understand you right, you want gnomon like a 
  light-spot.
  On my 
  sundial. I had the discs parallel with the wall, and if the discs are exact 
  parallel the shadows will be a circles too. 
  
  And the 
  hole (d=15mm) will be a circle too. 
  Look at 
  my homepage: 
  http://www.123hjemmeside.dk/tl-solur 
  
  And the 
  Danish Newspaper “Jyllandsposten”:
  http://www.jp.dk/kbh/artikel:aiid=3730350:img=0/
   
  And from Rødovre centrum:
  http://www.rodovrecentrum.dk/default.asp?id=264
   
  Best 
  regards and good Weekend.
   
  Thyge.
   
  --No virus found in this outgoing message.Checked by 
  AVG Free Edition.Version: 7.1.392 / Virus Database: 268.6.1/343 - Release 
  Date: 18-05-2006
  
  

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Re: Discs + holes, Sundiale near Cph.

[Chris Lusby Taylor]

(Sorry all. I just sent this with my date set to May 2005, 
to calculate the sun's position. That's twice I've done that in one week! 
Profuse apologies. Chris)
 
Hi Thyge,
Thank you for your contribution to this interesting 
debate. Your sundial is stunning. Trust the Danes to show the rest of the world 
how to apply good modern design ideas to old products.
 
Yes, we had realised that a circular disk parallel to the 
wall would cast a circular shadow. The issue was what happens, especially 
to the image of the circular hole in the middle of the disk, when the angle of 
incidence to the wall is very small. Your dial overcomes this, very sensibly, by 
limiting the width of each dial but having one on each face. Thus the sun is 
only on each dial for about 3 hours either side of when it is directly in front 
of the dial. So you never have the problem that John Shepherd 
described.
 
But imagine if your East-facing dial went back much 
further towards the shopping centre. Then, towards noon the shadow would become 
very long and indistinct. Also, the hole in the middle would become 
noticeably elliptical. John's point is that you are then better off with 
two intersecting lines. I'm inclined to agree with him, though I am somewhat 
surprised at the poor shadow he photographed just three hours before noon. In my 
experience a disk is quite usable over a longer time than that. Your photo of 
your east-facing dial on 3rd May at 11:02 shows the disk very clearly, even 
though the sun's azimuth was only 43 degrees east of south.
 
On of my favourite dials is the bifilar, but I had doubted 
whether people would understand and accept reading the intersection of two 
shadows. John encourages me to think they will.
 
Best wishes
Chris
51.4N, 1.3W
 

  - Original Message - 
  From: 
  Thyge Lauritsen 
  To: sundial@uni-koeln.de 
  Sent: Saturday, May 20, 2006 1:05 
AM
  Subject: Discs + holes, Sundiale near 
  Cph.
  
  
  Dear all members.
  If I 
  understand you right, you want gnomon like a 
  light-spot.
  On my 
  sundial. I had the discs parallel with the wall, and if the discs are exact 
  parallel the shadows will be a circles too. 
  
  And the 
  hole (d=15mm) will be a circle too. 
  Look at 
  my homepage: 
  http://www.123hjemmeside.dk/tl-solur 
  
  And the 
  Danish Newspaper “Jyllandsposten”:
  http://www.jp.dk/kbh/artikel:aiid=3730350:img=0/
   
  And from Rødovre centrum:
  http://www.rodovrecentrum.dk/default.asp?id=264
   
  Best 
  regards and good Weekend.
   
  Thyge.
   
  --No virus found in this outgoing message.Checked by 
  AVG Free Edition.Version: 7.1.392 / Virus Database: 268.6.1/343 - Release 
  Date: 18-05-2006
  
  

  ---https://lists.uni-koeln.de/mailman/listinfo/sundial
---
https://lists.uni-koeln.de/mailman/listinfo/sundial

Canadian Maritimes POI File for Sundial Tourists

[Richard Langley]

I have created a point-of-interest file containing the geodetic coordinates
and brief descriptions of some of the sundials in New Brunswick and Nova
Scotia, two of the Canadian Maritime Provinces. The initial sources of
information were Steve Lelievre's "Nova Scotia Sundial Trail"
 and the NASS Sundial Register
 plus various online mapping and other resources.

The text file has been created in a format which allowed conversion to a
TomTom Navigator software POI overlay file (with suffix .ov2). See
 for more
information.

The text file is easily read and could be converted to other GPS navigator
POI or waypoint file formats.

Attached are the small text and .ov2 files and a BMP icon which could be used
with the .ov2 file.

It would be useful for those of us who like visiting sundials on our vacations
to have sundial POI files for other regions. What is needed are accurate
WGS84 coordinates for the sundials or exact street addresses which can be
mapped to the coordinates.

-- Richard Langley

===
 Richard B. LangleyE-mail: [EMAIL PROTECTED]
 Geodetic Research Laboratory  Web: http://www.unb.ca/GGE/
 Dept. of Geodesy and Geomatics EngineeringPhone:+1 506 453-5142
 University of New Brunswick   Fax:  +1 506 453-4943
 Fredericton, N.B., Canada  E3B 5A3
 Fredericton?  Where's that?  See: http://www.city.fredericton.nb.ca/
===; Sundials in NB and NS Points-of-Interest (POI) Text File for TomTom Navigator

; Use MAKEOV2.EXE to create .ov2 file

; Created by Richard B. Langley, University of New Brunswick, 19 November 2005

; Longitude,Latitude, "Name"

; ==  




 -66.64093 ,   45.96205 , "Vertical Wall Dial, Soldiers' Barracks, Fredericton, 
NB"

 -64.21009 ,   45.83530 , "Pedestal Dial, Amherst Town Hall, Amherst, NS"

 -65.51581 ,   44.74222 , "Pedestal Dial, Historic Gardens, Annapolis Royal, NS"

 -64.24157 ,   44.53653 , "Armillary Sphere, Parade Square, Chester, NS"

 -64.30942 ,   45.11077 , "Horizontal Dial, Acadian Memorial Church, Grand-Pré, 
NS"

 -63.57431 ,   44.64362 , "Armillary Sphere, DalTech, Halifax, NS"

 -63.57855 ,   44.64317 , "Horizontal Dial, Halifax Public Gardens, Halifax, NS"

 -63.61490 ,   44.67549 , "Horizontal Dial, Seaview Memorial Park, Halifax, NS"

 -63.59218 ,   44.63629 , "Pedestal Dial, Quadrangle, Dalhousie University, 
Halifax, NS"

 -65.11979 ,   44.87788 , "Pedestal Dial, Whitman Cemetary, Williamstown, NS"

 -59.98763 ,   45.88903 , "Pedestal Dial, Engineer's House, Fortress of 
Louisbourg, NS"

 -65.07110 ,   44.94378 , "Horizontal Dial, Macdonald Museum, Middleton, NS"

 -63.83432 ,   44.89625 , "Pedestal Dial, Uniacke Estate Museum Park, Mt. 
Uniacke, NS"

 -64.37803 ,   45.11619 , "Pedestal Dial, Prescott House Museum, Starr's Point, 
NS"

 -64.13907 ,   44.98952 , "Pedestal Dial, Haliburton House Museum, Windsor, NS"

 -66.11557 ,   43.83651 , "Portable Dial, Yarmouth County Museum, Yarmouth, NS"



sundials.ov2
Description: Binary data


sundials.bmp
Description: Binary data
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