The Obelisk for the Horizontal Dial
Dimensions are given in centimeters.
Each side of the Obelisk faces one of the principal
compass directions and is designed with a unique time-related function,
to be made from custom ceramic tiles adhered to the
monument.
The South Face
has a vertical reclining Noon Analemma to show the
correction for the Equation
of Time or how many minutes the Sun is ahead or behind the Mean Time.
When the shadow of the tip of the style (Nodus) aligns with the appropriate
seasonal line-segment of the figure Mean Time Noon may be noted on the
Horizontal Dial from the shadow of the Obelisk. A model obelisk of the
same dimensions but with a Noon Analemma for 37.25 degrees latitude is
shown.
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The West Face
has an original I/O (Greek letter PHI) design from
which the A.M. time of Sunrise and the P.M. time of Sunset can be read
for each day of the year with marks for the first four weeks of each month
(1st, 7th, 14th, and 21st). The months are distributed around a circle
like the hours of a clock. The inner ellipse gives the length of daylight
to an accuracy commensurate within a few minutes/day by doubling the time
of sunset. Each space on the center scale marks a 10 minute interval. On
March 21st (Spring Equinox) the sun rises and sets exactly at 6:00 o'clock.
On March 31st, one might estimate Sunrise at 5:42 A.M. and Sunset at 6:18
P.M. The length of day would be 12 hours and 36 minutes.
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The North Face
bears a Sundial Epigram on Time in the form of an
acrostic (the initial letter of each line) spelling the name of the town.
REUTTE ACROSTIC
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Rechne
-
Einzelne
-
Umdrehungen;
-
Tageslicht
-
Trübsal
-
Entführt.
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A free translation in English would be:
-
Count rotations one by one;
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Daylight carries off gloom.
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The East Face
illustrates how to read the hour lines and the month
(zodiac) lines of the sundial laid out on the Isserplatz. It also shows
the observer the adjustment between Middle European Time and Middle European
Summer Time.
In addition, this face includes information on
the Longitude adjustment
and the correction for the Equation
of Time presented on an I/O original graph designed especially for
Reutte. The graph can be read for each day of the year with marks for the
first four weeks of each month (1st, 7th, 14th, and 21st). The months are
distributed around a circle like the hours of a clock. The vertical scale
gives the number of minutes where the date radius intersects the figure
which are added to the sundial time (Sun time) to convert to the Local
time (Earth time). For example, on April 14, 17 minutes would be added
to Sun time to determine the correct Earth time, while on October 14, an
addition of 3 minutes is required to correct the Sundial reading to the
proper local time.
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Construction Recommendations
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Position and stability of the base of the obelisk
are critical. Reinforced steel rods embedded in the foundation base to
rise the height of the obelisk should be considered. Concrete casting of
the obelisk in place should precede relayment of the pavement for precise
positioning of the hour and declination lines. A bolt to mount the sphere
to the top of the pyramid should be encased in the top of the obelisk shaft.
The pyramid itself can be free formed around the bolt. Note that the height
of the pyramid is one-half of its base width: this so-called golden
pyramid having the ratio of the sides for the triangle intersecting
the corner edge equal to the the square roots of 1(height) : 2(base) :
3(edge).
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Custom-made tiles can be produced from molds carved
in dampened plaster of Paris forms which when dry are filled with clay
slip. On hardening, the (greenware) tile must be biscuit fired in a kiln.
The bisque tile can then be painted with glaze and refired. The glazed
tiles can be mounted with commercial adhesive and grouted with any other
commercial tiles in any design configuration desired: standard rectangular,
cut and patterned, or broken for a random free-form layout or any combination
desired for an attractive, bright and colorful display. Tiles used in the
graphical displays can have thin lead caning inserted in the grout lines
to form black graph lines.
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For information about the Horizontal
Dial click here.
To return to the Home
page click here.
Page created by: Paul
E. Field
Page created by: Paul
R. Field
Changes last made on: September 10, 1998
Copyright (c) 1998 P. Field I/O Asso.