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Nearby Constellations

Nearby Constellations. (2-D “Constellations”, from Stars in 3-D !). Half-hour time exposure facing north & west. The stars are tracing counter-clockwise circles, centered on a point near the prominent North Star (Polaris). Notice the Big Dipper at the lower-left. “ Circumpolar ”

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Nearby Constellations

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  1. Nearby Constellations

  2. (2-D “Constellations”, from Stars in 3-D!)

  3. Half-hour time exposure facing north & west. The stars are tracing counter-clockwisecircles, centered on a point near the prominent North Star (Polaris). Notice the Big Dipper at the lower-left. “Circumpolar” Stars/Constellations This several-hour-long time exposure, taken from tropical northern Australia, shows the clockwise motion of the southern stars around the South Celestial Pole. (Photo by David Miller/DMI.)

  4. Earth shown at the center of the imaginary “Celestial Sphere”

  5. Celestial coordinates: “Declination” (d) and “Right Ascension” (R.A.) (=> “latitude” & “longitude”!)

  6. The Sun’s apparent path through the Celestial Sphere . . . (actually due to Earth’s annual orbit about the Sun!)

  7. “Summer Constellations” vs. “Winter Constellations”, due to Earth’s annual revolution about the Sun:

  8. Earth, Sun, and the “Zodiac Constellations” through the Seasons “Summer Signs” = “Winter Constellations”; “Winter Signs” = “Summer Constellations”

  9. An Earth-bound Observer sees only half the sky at any one time!

  10. “Time Zones” (artificial!), & some famous Meridians around the globe:

  11. “Northern” vs. “Southern” Celestial Hemispheres (& Northern/Southern Constellations!) (In Northern Winter/ Southern Summer…) =>

  12. What causes the Seasons?

  13. (“Summer” = Higher Sun and Longer Daytimes!)

  14. “Land of the Midnight Sun”? (Or the Noon Darkness…?)

  15. A good view from Stonehenge! (Sunrise on the Summer Solstice)

  16. Ancient “Observatories” in the Americas! (Serving as “Calendars” & “Almanacs”…)

  17. The Sun’s apparent path through the Celestial Sphere goes along the “Ecliptic Plane”… TILTED by ~23.5 with respect to Earth’s Rotation (NP/SP) Axis!

  18. More Tilt with respect to the Sun => Stronger Seasons!

  19. 1 Year  365.2425 Days  365.25 Days (Need “Leap Day” Corrections!) Christopher Clavius The lunar crater Clavius, with peripheral craters Pope Gregory XIII

  20. “Solar Days” (= a day “by the Sun”) (= 24 hrs.) vs. “Sidereal Days” (= a day “by the Stars”) (= 23 hrs., 56 min.) => 1 Year  365.25 Solar Days  366.25Sidereal Days

  21. “Precession” of Earth’s Axis, and the temporary nature of the “North Star” . . . . . . and the “Vernal Equinox”!

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