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Astronomy 101

Astronomy 101. Whats up there?. Stellar Magnitude. Stars are graded by how bright they are The brightest stars are stars of the 1 st magnitude. The dimmest stars you can see (with just your eyes) are stars of the 6 th magnitude.

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Astronomy 101

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  1. Astronomy 101 Whats up there?

  2. Stellar Magnitude Stars are graded by how bright they are • The brightest stars are stars of the 1st magnitude. • The dimmest stars you can see (with just your eyes) are stars of the 6th magnitude. • A star of the 1st magnitude is 100x brighter than a star of the 6th magnitude • Thus a star of the 2nd magnitude is 2.512 dimmer than a 1st mag star.

  3. Stellar Magnitude 0.03 Vega (chosen as the zero point) -1.47 Sirius (brightest star in the sky) -2.94 Maximum brightness of Jupiter -3.82 Maximum brightness of Venus -5.9 Brightness of ISS (space station) -9.50 Iridium flare -12.92 full moon -26.74 Sun

  4. Oh Be A Fine Girl Kiss Me

  5. What to look for? • Star clusters • Open clusters (M11) • Globular clusters (M13) • Nebula • Planetary (M57) • Dark (Horsehead Nebula) • Emission nebula (M42) • Supernova Remnant (M1)

  6. What to Look for?

  7. What to Look for? • Comets - Watch the web…. • Asteroids – Go to Minor Planet Center • Satellites – http://heavens-above.com • Planets • Inferior – Mercury, Venus • Superior – Mars, Jupiter, Saturn • Telescope – Everything else.

  8. List of things to look for • Messier catalog – 110 objects List of things that are not comets… • Caldwell catalog – 109 objects (list made by Patrick Moore) • Herschel 400 catalog (400 of the 2000 or so objects found by William Herschel) • NGC catalog - ~7000 objects

  9. Focal Ratio The focal ratio is the ratio of the light path to the size of the objective. My telescope has a 8” mirror, and a 50” light path. Thus the focal ratio is F/6 (F6.25)

  10. Magnification • The magnification of your telescope is the focal length of your telescope divided by the focal length of your eyepiece. • My 8” F/6.25 has a focal length of 50” = 1270 mm • My widest field eyepiece is a 32 mm. • SO: This gives me a magnification of ~40. • My 10mm eyepiece give me 127x. • Using my 2.5 barlow lens I can get 317.5x

  11. Field of view • Your dark adapted eye has a Pupil size of 4 to 9 mm • Eyepieces are sold by size (25 mm) and field of view (50 deg). • Field of view is Eyepiece FoV/Magnification • Thus, for my telescope 50/(1270/25) = 1 degree

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