It's often claimed that the fore-runners of mechanical clocks were physical
models of the heavenly sphere(s). In the northern hemisphere this/these
appeared to rotate clockwise. So clocks followed suit.
John Lynes
- Original Message -
From: Sumi Yoichi [EMAIL PROTECTED]
To:
Extending Roger Bailey's treatment, if you know the time and direction of
sunrise you can easily estimate the time and direction of sunset, or
vice-versa:
Time of sunset = 24 - (time of sunrise)
Azimuths of sunrise and sunset are equidistant from the North-South
meridian, remembering that
Two words were carelessly omitted from the third paragraph of my last
posting. Please accept my apologies. It's hard enough to digest even when
the wording is correct! Below is a corrected version of the posting:-
Extending Roger Bailey's treatment, if you know the time and direction of
Thanks, Fer. Apologies all round, and especially to
Anselmo. I now think his proposal would work after all. But only in
the winter months. At noon at the equinox the reflected beam would be
vertically above the mirror. During the summer months the beam would be
reflected south of the
In response to both Dave Bell and John Carmichael, I took the
small mirror as fixed, and required it only to be flat and, of course,
stable. These are necessary conditions for any ceiling
sundial.
My proposal does not require any knowledge of the actual
alignment of the mirror. John
Here's a simpler proposal.
Transfer the declination lines and hour lines of a horizontal
sundial onto a transparent sheet.
Mark a small circle on the centre of the mirror.
Support the horizontal transparent sheet, rotated from north
to south, with its nodusvertically above the centre of the
Here's an alternative approach, which would work best with two people:
Set up a simple horizontal sundial, with declination lines, correctly
oriented, beside the mirror, say a foot to one side.
Using a laser pointer, or just a bare low-voltage filament lamp, cast a
shadow of the gnomon onto the
Since nobody seems to have offered a reply to Albert's request
for a program to show shadows cast by buildings, may I offer a simple
suggestion?
Use any perspective drawing program. Arrange the
viewpoint to be at a large distance from the building, and in a direction
corresponding to the
Well spotted!My guess would be horizontal, southern
hemisphere.If vertical south-facing the Roman numerals would be upside
down seen frombelow.John Lynes
-Original Message-From:
John Davis [EMAIL PROTECTED]To:
sundial@rrz.uni-koeln.de
sundial@rrz.uni-koeln.deDate:
02 August 2000 08:54Subject: Transalpine
hours
Hi all,
I've come across a reference to transalpine
hours in Heilbron's
10 matches
Mail list logo