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Telescopes

Telescopes. 3 Functions 1. Gather light Size does matter The bigger, the better 2. Resolve detail 3. Magnification Only important for solar system objects. Refracting Telescopes. Cheap Good for bright objects Basic design. Reflecting Telescopes. Larger Size = Price

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Telescopes

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  1. Telescopes 3 Functions 1. Gather light Size does matter The bigger, the better 2. Resolve detail 3. Magnification Only important for solar system objects

  2. Refracting Telescopes • Cheap • Good for bright objects • Basic design

  3. Reflecting Telescopes • Larger • Size = Price • Fainter objects

  4. Catadioptric Telescopes • “Combination” • Shorter • Reasonable price • Common forms – Schmidt-Cassegrain (SCT) Maksutov-Cassegrain (Mak)

  5. Telescope Mounts • Alt-Az Mounts • Simple • Complex tracking • Fields rotate • Equatorial Mounts • Latitude dependent • Tracks easily • No rotation (good for long exposures)

  6. Telescope Details • Aperture = size of light gathering opening = D • Focal length = distance needed to focus light For the objective (the mirror/body of scope) = fo For the eye piece = fe • Magnification = fo/fe • Resolution, R = 12.0cm/D (result given in ′′) • For Catadioptric systems, objective is modified by correction plate.

  7. Taking Pictures • Film – 400 speed (ISO) • Digital – READ THE MANUAL • Long exposure times - stars, constellations • Short exposure times – Moon, planets • Brightness control, focus control, contrast control • Bracket!

  8. Camera Only • Constellations • Milky Way • Meteor showers • Aurorae • Long time = star trails • No trails: t = 30s – 1 m • Hazard: Fogging • Hazard: The Moon

  9. Prime Focus • Moon details (short exposure) • Telescopic objects (long exposure) • Digital – can “stack” multiple exposures • Magnification required for planetary detail • Adapter needed – “t-mount”

  10. 30 second exp. • 1600 ISO • 11 exposures • Stacked

  11. Piggy Back • Wide field, faint objects

  12. Afocal • Steady mount required

  13. Video • Regular video cams • Webcams • Security Cams • Speciality cameras • With t-mount or afocal • Software – stack images

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