Diese Nachricht wurde eingewickelt um DMARC-kompatibel zu sein. Die
eigentliche Nachricht steht dadurch in einem Anhang.
This message was wrapped to be DMARC compliant. The actual message
text is therefore in an attachment.
--- Begin Message ---
If you go to Kings College London, the Physics Department had a display
of some of Charles Wheatstone's equipment. This included a very
interesting Sundial that resembled a microscope. (I have a picture of it
from my days when I was there!) I never got a chance to take it out of
the cabinet to test it.
Julian
------ Original Message ------
From: "Maes, F.W." <[email protected]>
To: "Sundial Mailing List" <[email protected]>
Sent: Tuesday, 21 May, 2019 At 21:03
Subject: Wheatstone's polarizing sundial
Recently the Tesseract Catalogue 109 was announced on this list. Item
nr. 13 is a polarizing sundial by Charles Wheatstone. A virtually
identical dial is in the collection of the Greenwich museums, see:
https://collections.rmg.co.uk/collections/objects/265579.html
<https://collections.rmg.co.uk/collections/objects/265579.html> .
I have never understood how this sundial works. The hour scale shows 2 x
12 hour numbers in a semicircle. So whatever pattern is observed in the
black glass reflector, it is obviously supposed to rotate over 180° in
24 hours, which is half the angular velocity of the sun itself. How does
this frequency division-by-two come out? Can anybody explain?
Thanks!
Frans Maes
---------------------------------------------------
https://lists.uni-koeln.de/mailman/listinfo/sundial
<https://lists.uni-koeln.de/mailman/listinfo/sundial>
--- End Message ---
---------------------------------------------------
https://lists.uni-koeln.de/mailman/listinfo/sundial
