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Ch. 3 TELESCOPES

Ch. 3 TELESCOPES. INTRO. In astronomy, observation usually precedes theory . Ex/ New solar syst.; acc. univ. Telescopes have grown in size and complexity and now cover the entire EM spectrum. I. Optical Telescopes. A. Telescope : A “ light bucket ” used to capture

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Ch. 3 TELESCOPES

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  1. Ch. 3 TELESCOPES

  2. INTRO In astronomy, observation usually precedes theory. Ex/ New solar syst.; acc. univ. Telescopes have grown in size and complexity and now cover the entire EM spectrum

  3. I. Optical Telescopes A. Telescope: A “light bucket” used to capture incoming photons & concentrate them into a focused beam for analysis.

  4. B. Types of Telescopes • Refractors: A glass lens bends (refracts) incoming light rays to a focus. Eyepiecemagnifies.

  5. Yerkes Observatory

  6. 2. Reflectors: A curved mirror (the primary mirror) reflects incoming rays to a focus. Eyepiece magnifies.

  7. D. Reflector Design 1.Newtonian: Secondary mirror reflects light to side eyepiece. Subcategory: Dobsonian

  8. 2. Cassegrain: Secondary mirror reflects light back thru a hole in the primary mirror.

  9. II. Telescope Size & Resolution A. Light-gathering power: Larger collecting area - brighter image. 1. Brightness ~ Diameter2 Ex/ 10”apertureis 25 x brighter than 2”aperture (or 25 x faster exposure) 2. Largest: VLT in Chile (16 m) Keck I & II in Hawaii (14 m) TMT (2018); Giant Magellan Telescope (2016)

  10. Ch. 5 Example Problem How long would it take a telescope with a 9” aperture to produce the same image that a 3” scope can make in 45 min.?

  11. The VLT

  12. GranTeCan

  13. Canary Islands

  14. GMT: 7 8.4-m mirrors

  15. B. Resolving Power: Ability to make sharp images of faint objects or to distinguish between 2 adjacent objects in the sky.** aka Angular Resolution

  16. C. Atmospheric Blurring 1. Hinders ground-based scopes Ex/ “twinkling” stars 2. Best locations- high, dry, & dark Ex/ Arizona; Chile; Hawaii 3. Another solution - space. Ex/Hubble (1993) - 20 x better than previous best

  17. Pic Du Midi, French Pyrenees

  18. D. Adaptive Optics: Mirror changes shape to compensate for atmosphere. a. Lasers pierce atmosphere, create “artificial star” b. Some now sharper than Hubble! Ex/ Subaru (IR), Keck, VLT

  19. III. Radio Astronomy & Interferometry A. Radio telescopes 1. Only since the‘50’s Grote 2. Pioneers- Karl Jansky, Reber 3. Curved metal dish focuses radio waves to a focal point. 4. Instruments located at the prime focus.

  20. B. Large Size Necessary 1. Signals are faint 2. Long wavelength radio diffracts greatly - poor resolution a. Surface doesn’t have to be smooth like optical scopes b. It’s easy to make them large Ex/ Largest: Arecibo– 1000 ft. wide!(305 m)

  21. Green Bank, West Virginia - largest moveable radio dish

  22. C. Value of Radio Astronomy 1. 24 / 7 2. Thru clouds, rain, snow 3. Objects visibly dim may be strong radio sources. Ex/ *4. Radio penetrates dust in space. Ex/ Center of our galaxy

  23. D. INTERFEROMETRY 1. Interferometer: Data from 2 or more scopes combined. Ex/ VLA in N. Mex (27 dishes) ATA (2007)- 42 dishes ALMA (2012) - 66 Square Kilometer Array (2020) - 150 dishes 2. Behaves like a single dish whose diameter is the distance between dishes. Ex/ Compound eye

  24. Allen Telescope Array (so far..)

  25. Single Dish of the VLA

  26. VLA in New Mexico

  27. ALMA

  28. Largest Telescopes 2015

  29. A. Microwave satellites IV. Space Telescopes • COBE (1990’s) - Measured the cosmic microwave background Proof of the Big Bang! 2. Planck (2009)

  30. B. INFRARED Astronomy 1. Long wavelength IR penetrates clouds in space. 2. Good for star or planet-forming clouds of warm dust & gas. 3. Mountaintops Ex/ Subaru 4. Airplanes Ex/ SOFIA 5. Or Space Ex/ Spitzer James Webb Space Tel. (2018)

  31. SUBARU

  32. SOFIA

  33. James Webb Space Telescope“Successor to the Hubble” ~ 6.5 m mirror Launch in 2018 (?) Infrared

  34. C. Visible light: 1.Hubble Space Telescope 2. Spherical aberration corrected 1993 3. Final repair mission 2009

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