Astrophotography by Keith B. Quattrocchi

                 NGC 6781
                                           Planetary Nebula in Aquila                          
                   Narrow Band Image: (Ha-NII-OIII)
                     Published:  Astronomy Gallery March 1, 2010
                        Copyright 2009
                      Keith B Quattrocchi


                                      Image Acquisition Information                      
                               Telescope:   16" RCOS Richey Chretien Telescope (ion milled at 6/9) 
                               Camera:       SBIG STL-6303 M
                               Guiding:       SBIG AOL,  Astrodon  MOAG AOG (SBIG 237 with Custom FLR)
                               Filters:        Astrodon Ha, NII, OIII (3 nm filters)
                               Mount:        Software Bisque Paramount ME
                               Acquisition Programs:   The Sky,CCDAutopliot III, CCD Soft. 
                               Processing ProgramsCCDStack, Maxim DL, Photoshop
                               Date: August 26, 2009 -September 20, 2009,                              
                               Time: 10 x30 min ( 5 hours) each for each of Ha, NII and OIII:
                               Total of  15 hours imaging time.                              
                               Processing:  CCD Stack and PhotoShop CS/3
Image Infornmation:  NGC 6781 ia a planetary nebula in the constelation of Aquila.  It is 109 arc-secs in size at magnitute 11.4.  This object has distincively different patterns under NII and H-alpha filters, with a large central blue (OIII) component with minimal contribution in the SII region. It it about 3000 light-years distant.  The central star is faint at magnitude 15.5.
  Additional Comments:  This Narrow Band image was obtained using  AstroDon 3nm band pass of Ha, NII and OIII.  This object sheds light in the Ha, NII and OIII wavelengths, making it an interesting object for an NII filter.   The Narrow Band image was created by an unequal weighting of Ha/NII/OIII at a ratio of 1:1:4 (the OIII signal is relatively weak, but Ha and NII quite similar in strength, thought the pattern was different).   This was essentially a modified Hubble Palette (RGB as Ha/NII/OIII).   This was layered over a modified (enhanced) H-alpha image to bring out some of the details lost in the assembled narrow band image.   Further data stretching, high pass filtering and background smoothing was performed with Adobe Photoshop CS/4.  All data stretching was by minimal stretching with gamma and DDP in CCD Stack and then further stretching with curves/levels in photoshop.   

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