Simple shadow casting sundials
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Simple Shadow Casting Sundials. By Dr. Harold Williams of Montgomery College Planetarium http://montgomerycollege.edu/Departments/planet/. All Sundials. All sundials tell time by the position of the sun in the sky. Mostly they tell local apparent sun time.

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Simple shadow casting sundials l.jpg

Simple Shadow Casting Sundials

By Dr. Harold Williams

of Montgomery College Planetarium

http://montgomerycollege.edu/Departments/planet/


All sundials l.jpg
All Sundials

  • All sundials tell time by the position of the sun in the sky. Mostly they tell local apparent sun time.

  • At sunrise the sun is just coming up on the horizon.

  • At midday, noon, the sun is crossing the meridian, the line that runs from north to south through the zeinth, (the point over head).

  • At sunset the sun is just going down on the horizon.


Most sundials l.jpg
Most Sundials

  • Most sundials work by casting shadows with a “gnome,” shadow caster.

  • The shadow is projected on a surface that is a dial face telling you the time.


Equatorial sundial with gnome pointing toward the pole l.jpg
Equatorial Sundial with Gnome pointing toward the pole





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The Sun reaches its

Zenith (Peak) at

High Noon…

NOT!

The Sun Peaks in Takoma Park at

12:16 PM EST on March 18, 2006

Corrections:

1) Daylight Savings

2) Time Zones

3) Earth’s 23.5o Axis Tilt

4) Earth’s Elliptical Orbit



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Some Sundial Patterns for Here

  • Analamic & Horizon Sundial for 39 North http://www.montgomerycollege.edu/Departments/planet/sundials/analamic_&_horizontal39.pdf

  • Analamic Sundial for 39 North http://www.montgomerycollege.edu/Departments/planet/sundials/ana39.pdf


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Some Additional Sundial Resources

  • North American Sundial Society http://sundials.org/

  • British Sundial society http://www.sundialsoc.org.uk/

  • Sundials on Mars http://www.astrobio.net/news/article625.html


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