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

2. It’s Nebula Season Not many galaxies around….. 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 LinesAtomic 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/ http://www.sharplesscatalog.com/ Reiner Vogel’s Sharpless Observing Atlas: http://www.biophysik.uni- freiburg.de/Reiner/ATM/Sharpless/Sharples s_e.htmlhttp://www.biophysik.uni- freiburg.de/Reiner/ATM/Sharpless/Sharples s_e.html (Sharpless_Atlas.pdf) |Sharpless_Atlas.pdf