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Celestial Sphere Notes

Celestial Sphere Notes. Altazimuth Coordinate . Altitude Degrees above the horizon 0 ° to 90 ° Azimuth Degrees right of North 0 ° to 360 °. Altazimuth Coordinate. Horizon Zenith Meridian. Coordinate System. Celestial Sphere. Extension of our globe North/South Pole Equator.

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Celestial Sphere Notes

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  1. Celestial Sphere Notes

  2. Altazimuth Coordinate • Altitude • Degrees above the horizon • 0° to 90° • Azimuth • Degrees right of North • 0° to 360°

  3. Altazimuth Coordinate • Horizon • Zenith • Meridian

  4. Coordinate System

  5. Celestial Sphere • Extension of our globe • North/South Pole • Equator

  6. Celestial Coordinate • Latitude • Declination • Degrees above or below the equator • Longitude • Right Ascension • Hours to the right of north

  7. Both

  8. Real and Apparent Motion

  9. Apparent Annual Motion • Caused by the Earth revolving around the Sun • Causes Sun to shift position against the stars by about one degree per day (360/365).

  10. Apparent Diurnal Motion • Caused by the rotation of the earth • Causes everything in the sky to rise in the east and set in the west • Video

  11. Length of Day • Sidereal (Stars) • 23hr:56min • Relative to the stars • The correct one • Synodic (solar) • 24hr • Relative to the sun • The one we use

  12. Length of Month • Sidereal (Stars) Synodic (Solar) • 27.3 d 29.5 d • Relative to the stars Relative to the sun

  13. Length of Year • Defined as when the Sun on the ecliptic crosses the Celestial Equator.

  14. Precession • The Earth wobbles like any other gyroscope • Period = 26,000 yrs • Therefore the position of the sun relative to the stars changes slightly every year.

  15. Tropical Year • 365.24 days • Mean Solar Year • Sun at moment of spring to next crossing.

  16. Julian Year • 365.25 days • The one we use • Also a Julian Day • Stared on 1/1/4713BC • Today’s Date

  17. Sidereal Year • 365.26 days • Star at moment of spring to next crossing.

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