Sun Sky Solar Angles

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Sun / Sky / Solar Angles

• Day, Seasons and Sky Conditions

Chad Brossman
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Key Terms

• Longitude- Angular distance on the earth's
  surface, measured east or west from the prime
  meridian at Greenwich, England, to the meridian
  passing through a position, expressed in degrees
  (or hours), minutes, and seconds.
• Latitude- The angular distance (north or south)
  from the earths equator, measured in degrees
  along a meridian.
• Meridian- An imaginary circle on the globe
  passing through the (north and south) geographic
  poles. All points on a particular meridian have
  the same longitude.
• Tropic of Cancer- The parallel of latitude 2327
  north of the equator, the northern boundary of
  the Torrid Zone, and the most northerly latitude
  at which the sun can shine directly overhead.
• Tropic of Capricorn- The parallel of latitude
  2327 south of the equator, the southern
  boundary of the Torrid Zone, and the most
  southerly latitude at which the sun can shine
  directly overhead.

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Key Terms- Contd.

• Solstice- June 21st and December 21st
  (approximately, in the Northern Hemisphere).
  This is when the sun is at its greatest distance
  from the celestial equator. The summer solstice
  is the longest day of the year (noted as being
  when the sun is in the zenith at the tropic of
  Cancer) and the winter solstice is the shortest
  (noted as being when the sun is over the tropic
  of Capricorn).
• Equinox- September 21rd and March 21rd. When the
  sun rises due east and sets due west globally.
• Magnetic Declination- The difference between true
  north and magnetic north.
• Daylight Savings Hours- Locations which set
  clocks forward/back during the summer months.

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Key Terms- Contd.

• Azimuth- Is the compass bearing, with north being
  0 and south being 180, etc. Generally measured
  clockwise. Expressed by the angle alpha.
• Altitude (Solar) - is the sun measured from 0 on
  the horizon to 90 degrees at the zenith.
  Expressed by the angle gamma.
• Zenith- The point of the sky directly above you.
• Time- Used to determine the suns position (or
  vise-versa) Can be combined with the azimuth,
  altitude and day of year to determine precise
  solar angles at a given position. (solar, civil,
  standard are all variants).
• Twilight (sunrise/sunset)- The time period
  between visible sunlight and total darkness.
  Length of twilight varies by about 15 minutes
  depending on latitude. Noted as being when the
  sun reaches civil (6 below the horizon),
  Nautical (12 below) and Astronomical (18 below)
  twilights.

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Charts / Diagrams
56 degrees North Latitude
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Seasonal Effects

• Seasons- are relative to the suns position in the
  sky (the earths relation to the sun in orbit).
• Solar heating/Cooling is affected due to the
  intensity and amount of sunlight on a given
  surface used for thermal conditioning.
• Changes in weather and temperature.
• Differences in the length of shadows for any
  given time of day.
• Length of the day from sunrise to sunset.

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Sky Conditions

• Clouds / weather affect temperature. For example
  you can get a sunburn on a cloudy day.
• Sky conditions affect the dispersion of light
  rays and the intensity of light.
• Solar diffraction, the scattering of the suns
  rays due to air, suspended mater, dust, etc. in
  the atmosphere.
• Seasonal and Sky examples.

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Seasonal- Solar Eclipse

• Movement of moon and earth causes umbra to create
  a path on the globe.
• Sun is 400 times larger than the moon, but it is
  also 400 times further away, thus during an
  eclipse they appear to be the same size (within
  the umbra zone). Appearance of a partial eclipse
  will occur in penumbra zones.

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Sky Condition- Aurora Borealis

• The source of the auroras is the sun. The sun
  gives off high-energy charged particles (also
  called ions) that travel out into space at speeds
  of 200 to 440 miles per second. A "cloud" or gas
  of such ions and electrons is called plasma. The
  stream of plasma coming from the sun is known as
  the solar wind. As the solar wind interacts with
  the fringes of the earth's magnetic field, the
  particles are "shocked" into flowing around the
  earth. Some of the particles are trapped by the
  earth's magnetic field. They follow the magnetic
  lines of force down to the ionosphere. The
  particles strike the gases in the ionosphere,
  causing them to glow. The colors correspond to
  the different gases in the ionosphere. Oxygen
  atoms give off red and green light, depending on
  how high they are in the ionosphere. Nitrogen
  molecules give off blue and violet light. The
  aurora, a permanent feature of the earth's upper
  atmosphere, is actually a hollow oval centered on
  the geomagnetic poles. The size and shape of the
  auroral oval changes depending on how hard and
  how fast the solar wind from the sun is blowing.
  When the sun is quiet and the solar wind is calm,
  the auroral oval is small and thin. When the sun
  becomes more active and the solar wind hits the
  earth's magnetic field with strong gusts, the
  auroral oval becomes wider and stretches south.

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Architectural Examples

• Attempts to harness the power and grace of the
  sun (and heavens).
• Recognizing the importance of solar cycles,
  particularly the seasons of the year.
• Understanding the effects of the sun in relation
  to architecture.
• Source of inspiration and enlightenment.
• Historical and Modern Examples.

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Historical Precedence

• Egyptian Pyramids.
• Giza Egypt 2600-2480 BC.
• Architect unknown.
• Solar angles.
• The sun was used as a function of religion. It
  was said that one day of the year the sun would
  completely penetrate the light shaft and connect
  the pharaoh to heavens so that the pharaoh could
  travel to the gods in the heavens and eternal
  life.

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Khufus Pyramid, Egypt.
Section Drawing
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Historical Precedence

• Stonehenge
• Salisbury, England 2750-1500 BC.
• Architect unknown.
• Orientation, Lat 51 degrees 11 min north.
• While the exact function of Stonehenge remains a
  mystery (religious, agrarian, other) what is
  known is that it was deliberately orientated so
  that the mid summers morning sun rose over the
  heel stone, allowing the first rays of light to
  cascade into the center of the monument between
  the open arms of the horseshoe arrangement.

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Stonehenge England
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Modern Examples

• Phoenix Library.
• Phoenix AZ 1989-1995.
• Will Bruder and Ove Arup.
• Utilizes secondary functions to block thermal
  gain from the sun.
• Utilizes North/South faces for glazing.
• Candlestick columns, ignite (light up) on the
  solstice.

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Phoenix Library
Candlestick columns
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Modern Examples

• LInstitute du Monde.
• Paris, France 1987-1988.
• Jean Nouvel
• Shading
• Electronically controlled metal louvers adjust to
  control, or allow for a specific amount of direct
  light. Louvers work similar to the shutter in a
  camera.

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LInstitut du Monde Arabe, Paris