When a mirrored sphere is viewed or photographed from a sufficient distance,
the
size of the distorted image of objects reflected will be proportional to the
solid angle that they subtend at the centre of the sphere. In terms of
cartography, the reflection is an "equal-area projection". This
Dear Patrick,
Thank you for drawing our attention to Google's Art Project and The Ambassadors.
My guess about the object behind the shepherd's dial is that it is one foot of
the support for the celestial sphere.
Have you seen a delightful paperback, The Ambassadors' Secret, about this
painting
English Heritage has just revamped its searchable National Heritage list. 681
sundials are now listed and described. See
www.english-heritage.org.uk/list
Apologies to those who knew of this already!
John Lynes---
https://lists.uni-koeln.de/mailma
Dear Alison
One expedient, at least in theory, would be to fix a plane mirror,
suitably angled in plan to the main driveway and tilted to convert the
analemmatic sundial ellipse into a circle. The position of the human
gnomon would not vary with the season. The sundial would receive
reflect
Sorry, folks. As always, Chris Lusby Taylor is right. And as usual I have egg
on my face. I guess it’s a privilege to be mentored by such a precise and
patient authority.
Back to the drawing board. Here’s my next proposal:
Lay out a conventional analemmatic sundial turned through 180 degree
Forgive me, for returning with yet another tiresome proposal:
On reflection I suspect Mr Phillips may not be totally wrong-headed. On any
one day the azimuth of the shadow of a static human shadow-caster can be marked
by a circular arc of hour-marks or indeed by hour-marks fixed along two
stra
Dear Frans,
I happily endorse all your suggested improvements. I'd add the possibility of
using 3M's retro-reflective material, as on traffic signs, on the hour-markers
or, if the layout is reversed on the centre-post.
I just hope Mr Phillips appreciates all the hard thinking we've done on his
Dear Lloyd
Sunlight and shadow can be harnessed to provide warmth in winter and shade in
summer. Solar geometry, i.e. gnomonics, is the name of the game. This is of
course the basis of passive solar architectural design.
In the northern hemisphere a south-facing window can be protected by a c
Note that the hour markings will be reversed about solar noon. In the northern
hemisphere the shadow moves anticlockwise on a vertical surface.
John Lynes
--- On Wed, 10/9/08, The Thurstons <[EMAIL PROTECTED]> wrote:
> From: The Thurstons <[EMAIL PROTECTED]>
> Subject: RE: Vertical South dial
In his charming (but not always accurate) book "Light and Colour in the Open
Air" (Bell, 1959), which was earlier published as a Dover paperback, M.
Minnaert mentioned several multiple sightings of the green flash. He referred
to Byrd's expedition to the South Pole when the green flash could be
There's a whole family of architectural problems that require a knowledge of
dialling. For example -
* At what times will sunlight reflected from a tilted facade of
reflective glass be reflected into the eyes of motorists on a nearby road?
* What is the best configuration of fix
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