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History of Astronomical Instruments

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  1. History of Astronomical Instruments The early history: From the unaided eye to telescopes

  2. The Human Eye Anatomy and Detection Characteristics

  3. Anatomy of the Human Eye

  4. Visual Observations • Navigation • Calendars • Unusual Objects (comets etc.)

  5. Hawaiian Navigation: From Tahiti to Hawaii Using the North direction, Knowledge of the lattitude, And the predominant direction of the Trade Winds

  6. Tycho Quadrant

  7. Pre-Telescopic Observations • Navigation • Calendar • Astrology • Planetary Motion • Copernican System • Kepler’s Laws

  8. Why build telescopes? • Larger aperture means more light gathering power • sensitivity goes like D2, where D is diameter of main light collecting element (e.g., primary mirror) • Larger aperture means better angular resolution • resolution goes like lambda/D, where lambda is wavelength and D is diameter of mirror

  9. Refractor telescopes exclusively use lenses to collect light have big disadvantages: aberrations & sheer weight of lenses Reflector telescopes use mirrors to collect light relatively free of aberrations mirror fabrication techniques steadily improving Collection: Telescopes

  10. William Herschel Caroline Herschel

  11. Herschel 40 ft Telescope

  12. Basic optical designs: Prime focus: light is brought to focus by primary mirror, without further deflection Newtonian: use flat, diagonal secondary mirror to deflect light out side of tube Cassegrain: use convex secondary mirror to reflect light back through hole in primary Nasmyth focus: use tertiary mirror to redirect light to external instruments Optical Reflecting Telescopes

  13. Mirror Grinding Tool

  14. Mirror Polishing Machine

  15. Fine Ground Mirror

  16. Mirror Polishing

  17. Figuring the Asphere

  18. Crossley 36” Reflector

  19. Yerkes 40-inch Refractor

  20. Drawing of the Moon (1865)

  21. First Photograph of the Moon (1865)

  22. The Limitations of Ground-based Observations Diffraction Seeing Sky Backgrounds

  23. Diffraction

  24. Wavefront Description of Optical System

  25. Wavefronts of Two Well Separated Stars

  26. When are Two Wavefront Distinguishable ?

  27. Atmospheric Turbulence

  28. Characteristics of Good Sites • Geographic latitude 15° - 35° • Near the coast or isolated mountain • Away from large cities • High mountain • Reasonable logistics

  29. Modern Observatories The ESO-VLT Observatory at Paranal, Chile