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Astronomy Instrumentation

Astronomy Summer School for West Africa. Astronomy Instrumentation. Daniel Okoh. Outline:. Telescopes. Telescopes. Telescopes. Astronomy Instrumentation. Telescopes: What are they?. They are instruments that enable us ‘see’ distant objects by gathering ‘light’ from them.

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Astronomy Instrumentation

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  1. Astronomy Summer School for West Africa Astronomy Instrumentation Daniel Okoh

  2. Outline: Telescopes Telescopes Telescopes Astronomy Instrumentation

  3. Telescopes: What are they? They are instruments that enable us ‘see’ distant objects by gathering ‘light’ from them Astronomy Instrumentation

  4. Telescopes: What are they? Optical Telescopes Radio Telescopes Astronomy Instrumentation

  5. Optical Telescopes They come in various sizes and form Astronomy Instrumentation

  6. Optical Telescopes: Basic Operation Objective Eye piece Astronomy Instrumentation

  7. Optical Telescopes: Basic Operation Astronomy Instrumentation

  8. Radio Telescopes They need to be big! Really really big!! Astronomy Instrumentation

  9. Why? The Quest for more! Oliver Twist θ = λ D Astronomy Instrumentation

  10. Telescopes in Space Windows and Walls Astronomy Instrumentation

  11. Telescopes in Space Hubble Space Telescope Astronomy Instrumentation

  12. Angular sizes in astronomy θ Astronomy Instrumentation

  13. If the same object is farther away, the angular size is smaller θ1 θ2 Astronomy Instrumentation

  14. Objects of different linear sizes can have the same angular sizes θ Astronomy Instrumentation

  15. Activity 1: Estimate the angular size of your full fist at arm’s length Astronomy Instrumentation

  16. Activity 1: Estimate the angular size of your full fist at arm’s length Astronomy Instrumentation

  17. Activity 1: Estimate the angular size of your full fist at arm’s length θ θ y x x tan θ = x/y 2θ = 2 tan-1 (x/y) Astronomy Instrumentation

  18. Activity 1: Estimate the angular size of your full fist at arm’s length Astronomy Instrumentation

  19. Small angle approximation A d D A = D/d * 57.3 degrees Astronomy Instrumentation

  20. Activity 2: Angular size of the Sun A 1.4*106 km A = ?? 1.5*108 km Astronomy Instrumentation

  21. Activity 2: Angular size of the Moon A 3,475 km A = ?? 384,400 km Astronomy Instrumentation

  22. 0.5 degrees! for both Sun and Moon Sun and Moon same size? Eclipse Implication? Fist or finger to block out the Moon? Astronomy Instrumentation

  23. Telescope Resolutions 2 degrees!? Astronomy Instrumentation

  24. Why Radio Telescopes should be larger than optical telescopes θ = λ D Astronomy Instrumentation

  25. Activity 3: What Radio = Optical telescope ? A 25 cm Optical Telescope will have same resolution as a …… cm Radio Telescope Assume Optical Telescope λ = 500 nm And Radio Telescope λ = 6 cm 30 km ?? Astronomy Instrumentation

  26. VLBI (Very Long Baseline Interferometry) Astronomy Instrumentation

  27. Radio Antenna Surfaces Astronomy Instrumentation

  28. Radio Antenna Surfaces Astronomy Instrumentation

  29. Steering in Azimuth And Elevation Where we have to look to see stars and other objects 0 10 45 90 Astronomy Instrumentation

  30. Steering in Azimuth And Elevation 0 10 45 90 Astronomy Instrumentation

  31. Radio Telescope Receivers Similar in many ways to other receivers we use for TV and other radio collections Major difference: Astronomy signals are really very weak compared to other terrestrial signals What constitutes noise is therefore high Signal to noise ratios can be reduced by reducing receiver temperatures There is need to cool the receivers to really low temperatures Astronomy Instrumentation God Dependent Cryogenic

  32. The Address of stars: Right Ascension Declination Room 105 Department of Physics & Astronomy University of Nigeria Nsukka Enugu State Nigeria Astronomy Instrumentation

  33. Celestial Equator

  34. Activity 4: Telescope Pointing Determine the direction (azimuth and elevation) a telescope should point this evening at 6:34 PM to be able to observe α – Centauri from here in Abuja. Assume 2 telescopes at Nsukka and Abuja are to be used for VLBI observations of Sirius at 8:22 AM tomorrow morning. At what directions should each of the telescopes point? Will it be possible to join a telescope at Nanshan, China to this VLBI observation? What about a telescope at Cape Town, South Africa? Astronomy Instrumentation

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