I knew you'd write back John!
Loved your comments. "High Noon" is a very
common and still used _expression_ here in the American Southwest. (In lots
of old cowboy movies that's when they have the shootouts. They probably only had
sundial and noon marks back then). It's a favorite of mine, so much so
that I engraved my Flaundrau Planetarium heliochronometer with a High
Noon Mark. (again, more guilt feelings!) I'm sure it indicated the
time when the sun crosses the N/S meridian and is at its daily highest point,
not when it reaches zenith. And it certainly is not when a clock says 12:00
pm. So you could use this term anywhere in earth, not just tropic latitudes
where the sun reaches zenith.
Also, I forgot to mention "Beaded Figure-eights"
(Analemmas who's dates/declinations are marked).
And by popular demand, everyone, especially Steve
Lelievre, Fred and Fer will pleased that I don't say "Singleton Dial"
anymore!
John
John L. Carmichael Jr. Sundial Sculptures 925 E. Foothills
Dr. Tucson Arizona 85718 USA
----- Original Message -----
Sent: Friday, August 17, 2001 11:36
AM
Subject: Re: Sundial Slang
Hi John et al,
I couldn't let this pass without comment :-)
!!
I'm not sure that I am in any position to "approve" the
correct terms - the BSS Sundial Glossary is just a collection of the bits of
information that I've pulled together from various sources, including much
input from the participants of this list. I have no problem with the use
of slang terms, especially when they help those poor unfortunates that aren't
sundial enthusiasts know what we're talking about. It does need care,
though, not to introduce or reinforce misapprehensions. Most of John's
terms seem to avoid this, though whether they are more easily understood than
the "scientific" term is debatable.
One term which is common and not (yet) in the Glossary
is "High noon". Is this an americanism? I have, of course, seen my
cowboy movies, but am unclear where the term originates. Is it that,
with the relatively low latitudes in the south of America, the Sun can come
close to directly overhead (altitude = 90 degrees) at noon? If so, it
reinforces the wrong view of much of the UK media that the Sun is at the
"zenith" at noon. Whilst many ordinary people think of "zenith" as the
highest point of the arc, astronomically it is defined as the point which
really is directly overhead (only expressed rather more
formally!).
Another point to watch is the use
of "due north" instead of celestial pole. If you are at northerly
latitudes, the difference between celestial and geographic north can be
significant. Why not use the Pole Star as a better everyday
approximation?
"Horizon pollution" is an
interesting term. I guess we would define this as a percentage of the
daylight period when the Sun falls on a particular site. It's difficult
to come up with a mathematical definition, as it depends on the Sun's
declination as well as the positions of any obstructions. Do we know of
any dials at locations which can show the time over the full sunrise-sunset
period thoughout the year?
Regards,
John
------------------------------------------------------
----- Original Message -----
Sent: 17 August 2001 16:07
Subject: Sundial Slang
Hi All,
I've just finished the
7th edition of my Sundial Owner's Manual and realized that
throughout the manual I explained sundial terms using sundial slang instead
of the John Davis approved correct term. (Although at least in the Manual I
place the correct term next to it in parenthisis) I also use sundial slang
when I’m talking with others. I
feel a little guilty because I’m not using the correct terms. But the slang serves a very useful
purpose in that it is so intuitive and self-explanatory. (The sundial purists are going to
hate me for this!)
Anyway, here are a few of
them…
*High noon (Apparent
Noon)
Fuzz
zone (The penumbra)
Fuzz
factor (formula that determines the width of the penumbra: F=1/100) The
Correction graph (The Equation of Time)
Sun
height (solar altitude)
Sun
direction (solar azimuth)
Due
North (The Celestial Pole)
Sun
time (Apparent Time)
Watch
time (Standard Time)
Date
Ball (Spherical Nodus)
Shadow
caster (gnomon)
The
edge of the shadow caster (style)
Moontime (time shown by moon
shadows on a sundial)
Time
Zone correction (Longitudinal Shift)
Horizon
pollution (the objects around sundial that shade it from the sun. ie. trees, buildings,
mountains. No correct term for
this that I know of)
*As a sundial slang purist, I
get upset, like any good dialist would, when my favorite radio station
announces that it is High Noon (12:00 pm watch time), but because of our
Time Zone Correction, it’s really only about 11:30 am Sun time!
John
John L. Carmichael Jr. Sundial
Sculptures 925 E. Foothills Dr. Tucson Arizona
85718 USA
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