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What’s Up for Imagers

What’s Up for Imagers. The Sharpless Catalog January 2011 B. Waddington. It’s Nebula Season. Not many galaxies around….. <sigh> But plenty of good nebula opportunities Larger targets for shorter focal lengths Interesting structure for longer focal lengths Good narrow-band targets |.

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What’s Up for Imagers

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  1. What’s Up for Imagers The Sharpless Catalog January 2011 B. Waddington

  2. It’s Nebula Season • Not many galaxies around….. <sigh> • But plenty of good nebula opportunities • Larger targets for shorter focal lengths • Interesting structure for longer focal lengths • Good narrow-band targets |

  3. Hunting Nebula Targets • Just as the Arp catalog was a good resource for finding interesting galaxies… • The Sharpless catalog is a great resource for nebulas • Amateur contributions have made this especially easy to do |

  4. Sharpless Catalog • Developed by Stewart Sharpless at USNO in late 1950’s • Two increments (SH-1, SH-2) • 1953 – 142 objects using Palomar Sky survey plates (Baade & Minkowski) • 1957 – Final catalog of 313 objects using National Geographic/Palomar Sky Atlas • “Comprehensive” for Dec > -27° |

  5. Sharpless Catalog • Plates taken in both “red” and “blue”; color used to rule out reflection, planetary nebulas • Catalog included identification of related bright stars • A few “mistakes” – supernova remnants, planetary and reflection nebulas… |

  6. What Was the Point? • Map spatial distribution of hydrogen and regions of star formation in our galaxy • A good tool for building a model of Milky Way spiral arm structure • Also used to refine the galactic pole position |

  7. Quick Review of “HII regions” • HII – ionized hydrogen • HI – neutral hydrogen • H2 – molecular hydrogen • A little bonehead physics: Atomic Emission Spectra - the Origin of Spectral Lines|

  8. HII Region Behavior • Nearby bright OB stars ionize the interstellar hydrogen • Free electrons recombine with protons and release energy (photons) • Electrons “cascade” from higher to lower states, resulting in well-known emission lines • The Balmer series emission lines will be the major components in an amateur image of an emission nebula |

  9. Sharpless Object Locations

  10. Sharpless Object Sizes

  11. General Characteristics • Wide distribution of sizes, plenty of targets for all focal lengths • Plentiful in Winter and Summer (doh) • Good candidates for narrow-band imaging, especially H-alpha |

  12. Sharpless Catalog Usage • Includes many well-known objects – M42, Rosette, Lagoon, Cone nebulas… • But also provides a path to less well-known but interesting targets • “Shopping” is easy with some excellent amateur sites |

  13. Sharpless Resources • Dean Salman (“Mr. Sharpless”) : http://www.sharplesscatalog.com/ • Reiner Vogel’s Sharpless Observing Atlas: http://www.biophysik.uni-freiburg.de/Reiner/ATM/Sharpless/Sharpless_e.html (Sharpless_Atlas.pdf) |

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