(SNES) Gnomenology and the Astronomical Cognoscenti

["Les Coleman" <les11@cox.net>]

Hi,

I though you might get a boot out of what will become my November newpaper
column after a bit of polishing

Most of the time when we think about astronomy we think about stars,
planets, comets and galaxies, and well we should.  Maybe we think of the
tools of our trade, scopes, instruments, clocks, computers and software.
Yet I find it fascinating to consider the tools that no longer are used
except as curios and oddities.  I wrote a column long ago called Requium for
a Sextant about Naval Academy no longer offering instruction in naviagtion
by the stars.  Today I'd like to talk about the most lowly of the tools
developed by astronomers - the sundial.

It may come as a bit of a surprise but sundials are very complex objects, at
least if they try to achieve a bit of accuracy.  The Societe Astronomique de
France has a whole section of their society devoted to sundials - Commission
des Cadrans Solaires.  All this for the lowly birdbath with a gnomen
sticking out of it.  By the way, the word gnomen not only refers to the
stylus in a sundial's face but to person who looks at a sundial to see what
time it is.  Did you know you were practicing gnomenology when you glanced
at a sundial? [I recommend you only mention this odd behavior only in the
most discrete and liberal minded of company.]

Sundials can be oriented in almost any direction, but one which works just
fine lying horizontally will not work correctly if it is copied on the wall
of a building.  More than a few of these pretentious objet d'arts have had
to be rebuilt when they were bolted in place only to have the new owners
find that they didn't work at all!  A sundial which works in the northern
hemisphere tells time backwards in the southern hemisphere.

One of the most interesting sundials is the two sided sundial which keeps
time on the top side during the spring and summer and keeps the time on the
underside in fall and winter. The gnomen must pierce the sundial like a
shaft through a platter.  The dials can actually be arranged differently so
that the sundial keeps daylight savings time in spring and summer while
keeping standard time in fall and winter.  While they are wrong for a few
weeks between the time of the equinox and the time of clocks changing, it is
a clever trick for a sundial which isn't moved or reset.  How does this two
sided sundial work?
The trick is to orient the dial on a slant so that the gnomen is parallel to
the Earth's axis. The plane of the sundial will then be parallel to the
Earth's equator. When the Sun is above the equator, spring and summer, the
top side of the dial is
illuminated and vice versa for fall and winter. I wonder how many
astromomers with equitorial telescope mounts realize that if they left their
scope until sunrise, that their setting circles would become a sundial?

Les Coleman
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