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Astrophotography by Bob Franke

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NGC 6960 - The Witch's Broom

       Click the full screen zoom button           ^
Click the image to Zoom and Pan              

Click here to view the image without Zoomify (1913 x 1275 - 667 KB)





12.5" RCOS @  ~f/9 (2880 mm fl) 0.64 arcsec / pixel.  The Zoomify image scale is 1.28 to 3.26 arcsec / pixel.


Paramount ME


SBIG STL-11000 w/ internal filter wheel, AstroDon Gen I Filters

Acquisition Data

9/9/2010 to 10/26/2010 Chino Valley, AZ... with CCDAutoPilot3 & CCDSoft.  AOL guided


Ha                  540 min (18 x 30 min, bin 1x1)

OIII                540 min (18 x 30 min, bin 1x1)

Lum (no filter)  465 min (16 x 15 min, bin 1x1)

RGB                270 min ( 6 x 15 min each, bin 2x2)

Click here for the color mapped narrowband version.

Click here for an Ha filtered b/w image.


  • CCDSoft, CCDStack, Photoshop CS w/ the Fits Liberator plugin.

  • eXcalibrator for (b-v), (v-r) star color calibration, using 12 stars from the NOMAD1 database.

  • PixFix32 (pre-beta) to repair column defects.

  • CCDStack to calibrate, register, normalize, data reject,  combining the sub exposures and RGB combine

  • PhotoShop for non-linear stretching and sharpening.

  • Noiseware Pro, a PhotoShop plug-in


North is ~ to the left.  The image is rotated 70 degrees CCW.

The Western Veil, NGC 6960, commonly named The Witch's Broom, is part of the Veil Nebula, which is also known as the Cygnus Loop. The Veil nebula is located in the constellation, Cygnus, at a distance of about 1400 light-years. Its apparent size is more than five times the full Moon.

The Veil Nebula is a supernova remnant of heated and ionized gas. The source supernova exploded some 10,000 to 20,000 years ago. The expanding debris cloud gains its colors by sweeping up and exciting existing nearby gas.

Although this image was taken with narrow band filters it is a fairly good presentation of what the nebula looks like if red, green and blue filters were used. This is possible because the band width of the OIII filter is about half way between green and blue. This technique works especially well with this nebula because the RGB colors are mostly red and cyan. I used this method because, with true RGB, the stars completely overwhelm the nebula. Using narrowband filters also reveals greater detail.