The DeCordova Town Clock
N32.25.718 W097.42.102
The DeCordova Town Clock
indicates noon throughout the year and the day of year as well. In sum, it is a
calendar and a clock. It cost less than 26 cents to build. Please leave the
pennies and the silver Japanese Yen where you see them.
An "L" shaped shadow
is cast onto the concrete driveway by the sun passing behind the inside corner
of the house rain gutter. This is the clock's "Gnome".
A small black bar marks the 1st
day of each month. Pennies mark the 7th and 21st of each month.
The black line joins the
markings during the Winter and Spring season. The silver line joins the
markings during the Summer and Fall season. Both lines form a figure eight
shaped pattern. This is called an Analemma. (Ann-a-lee-ma) and is shown in the
left picture below.
|
|
|
DeCordova
Town Clock
Pictures taken on Dec 22, 2001. Left Photo was taken at 11:30 A.M. and
the right at noon. Note the one day movement from the Dec 21 yen marking the
day before and is moving to black cross bar New Years day. The sun moves faster
in the fall and winter than in the spring and summer.
The four silver Japanese yen mark the four seasons: Winter Solstice on December 21st, Spring Equinox on March 21, Summer Solstice on June 21st, and the Fall Equinox on September 21.
If you are here at noon any day of the year, the "L" shaped shadow will indicate the time of year with an uncanny degree of accuracy.
To see what your Analemma would look like go to the following web site. You can input your latitude and longitude. http://users.hartwick.edu/hartleyc/sundial/sundial.html
|
|
|
Above pictures were taken about noon on June 21, 2002. Left Photo shows the figure eight pattern of the Analemma. The right photo was taken at noon. (Not adjusted for Day Light Savings Time). The center area is now painted gray for clarity. The difference between the Dec 21 and June 21 shadow is 10 feet 8 inches.
We hope you enjoy the project.
BSS Sundial Glossary http://www.sundialsoc.org.uk/glossary/frameset.htm
Analemma
The analemma is a figure-8-shaped diagram that shows the declination of the sun
(the angle that the sun is from the equator), for each day in the year. If you
took a snapshot of the the sun at the same time each day (from the same
location), the Sun would make a figure shaped like an analemma during the
course of a year (this is because the Earth is tilted on its axis and because
it doesn't orbit the Sun in a perfect circle).
Links
to my favorite Analemma Sites
There is a
large collection that is on going on the www.geocaching.com web site at the following link:
The group name is a locationless cache with the sundial subject. If you know of
a sundial check to see if it is logged and if not add it to the collection.
(Added 01/27/04)
Richard D.
Swensen Analemma- University of Wisconsin, Fall River
http://www.uwrf.edu/sundial/welcome.html
http://www.uwrf.edu/sundial/design2.html
The
Physics-Astronomy Sundial, University of Washington
http://www.phys.washington.edu/pab.htm
A Simple
Vertical Gnomon Sundial to Read Time and Date by C. Hartley
http://users.hartwick.edu/hartleyc/sundial/sundial.html
The Missouri
Megalith, University of Missouri, Rola, MO
http://en.wikipedia.org/wiki/Missouri_University_of_Science_and_Technology
Stonehenge Clones and Metaphorms
http://www.luckymojo.com/stonehenge.html
Red Rock
Project (When you have more spare time than I do)
http://www.redrok.com/analemma.htm
Other Sites worth exploring:
http://www.sundials.co.uk/pix.htm
NASA Sundials
http://www.nasa.gov/lb/audience/forkids/activities/A_Make_a_Sundial.html
Paper Plate Education
http://analyzer.depaul.edu/paperplate/Sunrise%20Sunset.htm
Sun Rise Animation.
http://pages.prodigy.net/pam.orman/joesun/Sun_05.html
Archaeoastronomy Web Site
http://www.archaeoastronomy.com/index.shtml
Seasons of the Year
http://www-spof.gsfc.nasa.gov/stargaze/Sseason.htm
The active sun.
http://antwrp.gsfc.nasa.gov/apod/ap000608.html
Astronomy Picture of the Day Archive
http://antwrp.gsfc.nasa.gov/apod/archivepix.html
Making a Sundial
http://www.jgiesen.de/analemma/
http://www.autodidacts.f2s.com
http://solar.physics.montana.edu/YPOP/Classroom/Lessons/Sundials/sundials.html
http://www.kyes-world.com/sun.htm
|
Revised March 6, 2008 |
Designed by Phil Delucchi |