Re: Astronomy, art and sundials

[Chris Lusby Taylor]

Yes, I made one a few years ago and gave it to Giles Hudson at the Museum of the History of Science at Oxford. Although it was only made of card, and had been intended as a personal gift to him, he asked if he might put it in the museum's collection. It was to deduce the dial's geometry from the perspective view in The Ambassadors that I derived the surprisingly simple formulae that I sent to this list at the time. If anyone wishes, I can repost them. As for the dial and whether it would work, the answer seems to me to be that it would, but only at a latitude of about 22 degrees north. Professor North's book disagrees. I am fairly sure that the object in the upper face is a magnetic compass and that, therefore, that face must be horizontal in use. The gnomons would then all be inclined at about 22 degrees to the horizontal. The only significant place I can find with a latitude of about 22 degrees is Mecca. By the way, the painting seems to show that the end faces are square, but when you apply the formulae for calculating the edges, it turns out that it is rectangular, with an aspect ratio of around 0.85:1 (from memory). I put this down to Holbein's artistic licence and proof, if it were needed, that he did not use a camera obscura.   Merry Christmas to all Chris Lusby Taylor   ----- Original Message ----- From: Richard Hollands To: Sundial Sent: Thursday, December 23, 2004 9:07 AM Subject: Astronomy, art and sundials Talking of art and sundials (OK, I know. Close though). Has anyone ever attempted anything like the interesting polyhedral dial show in Holbien's "The Ambassadors"? If you don't know the picture it's here: http://gallery.euroweb.hu/art/h/holbein/hans_y/1535a/1ambassa.jpg I can imagine it being an interesting school project - in stiff card - if somebody provided a PDF file or similar to print out.I've had as close a look as you can expect to get using a computer image file (not forgetting the caveats about working from photographs) and it seems to me that Holbien has produced a picture of something  that would actually work. What do you think?  Richard