J Malecki wrote:
I've never been to Australia but I vaguely remember hearing that
at their swimming areas they have sundials with 3 circles of the
colors: green, yellow and red. The colors are (presumably) based
on the altitude of the sun and provide a indicator of the sunburn
danger.
The patent for a Ultraviolet Sundial can be found at the address
http://www.freepatentsonline.com/5576551.html
where a technical description is also available.
It looks like a horizontal dial with a vertical style and sun height lines
drawn for constant values of sun height, marked in
On Jun 13, 2010, at 12:16 PM, Jack Aubert wrote:
I have been working on photo-engraved brass dials under the generous
long-distance tutelage of Tony Moss, starting from a video that he presented
at our most recent NASS conference.
Is this video online anywhere? I'm curious about how the
