Eugene Astronomical Society Presentation  - February 15, 2012

Sun Position Fun

Observing and understanding the sun's position and movement,
indoors and outdoors, day and night

pisgah solstice sun monument
Daytime astronomy is fun, convenient, and can inform nighttime astronomy. We'll discuss observing the sun's daily and seasonal position and movement, outdoors and indoors, day and night, directly and indirectly. Topics include solar time, rise/set, daily movement, finding direction/time/position, moonlight, the annalemma, earliest sunset, sundials, and sun art. For example, understanding how the sun's azimuth and altitude change during the day is useful for orientation, and for knowing how the stars and ecliptic move at night. Methods and instruments to be discussed include sights, projection/reflection devices, planisphere, astrolabe, noon mark, shadow traces,  sun compass,  photography, imagination, and various kinds of sundials. Throughout, I'll suggest simple projects which will entertain, engage and educate family, friends and the public.

Homework

  1. When is the sun highest in the sky and due south today?  On February 15? Observe and/or compute.

  2. Observe the sun and moon together in the sky, e.g. around first quarter.  Should the illumination on the moon point to the sun?  Does it?  Why or why not?

Presentation Slides (pdf, slightly revised)

Handout

Contains solar noon table, equation of time correction table, and plotted analemma

Sun Motions Demonstrator

My Sun Bookmarks  

Search page for keywords, topics

Resources and Details (In Progress)

Includes links, notes, corrections, improvements and credits


  1. Introduction  - easisest star to observe; daytime astronomy, stars; uses; outreach.  A Brief History of Telling Time - and Sun Consciousness

  2. Background - sun movement in stars: chart;  sun movement in sky: animation

  3. Observing Methods

  4. Estimation

  5. Sun Sights and Project

  6. Solar Time and Noon Mark Project  - solar day; equation of time; solar time;  noon mark project 

  7. Daily Movement  - declination and hour angle;  rise/set: time, azimuth, angle; noon transit; hourly alt/az position and rates

  8. Altitude/Azimuth and Astrolabe -  ra/dec <->  alt/az;  planispheric astrolabe; extend to star movement

  9. Finding Direction - primitive direction finding; shadow trace; sun compasses; surveying Oregon

  10. Finding Location  - noon sight and navigation;  bird tracking by photoperiod

  11. Analemma - components; earliest/latest sunrise/sunset

  12. Sundials - gnomon; types; usability and design; embellishments; Eugene dials

  13. Sun At Night - imagination, anti-sun, ecliptic; moon age, moondial;   moon illumination

  14. Public Sun Instruments and Art

  15. Summary

Projects Incorporated Throughout

  1. Sun Sights -  e.g. sunset point, special event

  2. Noonmark and Solar Time

  3. Shadow Stick - telling time, curves, finding east-west

  4. Analemma - observe sun's position at given time throughout year

  5. Sundial - gnomon, time, embellishments

  6. Public Sun Instruments and Art

John Hartman, Ph.D.
Software Understanding
jh@softwareunderstanding.com
541-505-9980
2165 Adams St  Eugene OR  97405
softwareunderstanding.com