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Astrophotography by Bob Franke

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The Propeller Nebula

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

Click here to view the image without Zoomify (1875 x 1250)



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

Click here to view the image without Zoomify (1875 x 1250)



12.5" RCOS @  ~f/9 (2880 mm fl) 1.28 arcsec / pixel.  The Zoomify image scale is 1.28 to 3.20 arcsec / pixel.


Paramount ME


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

Acquisition Data

6/26/2010 to 7/15/2010 Chino Valley, AZ... with CCDAutoPilot3 & CCDSoft.  AOL guided


SII   480 min. (16 x 30 min. bin 2x2)
α    510 min. (17 x 30 min. bin 2x2)

OIII  570 min. (19 x 30 min. bin 2x2)

RGB  180 min. (  4 x 15 min each, bin 2x2)

SII:Hα:OIII mapped to RGB  with an overlay of RGB stars colors.

Click here for an RGB color version.

Click here for an Ha filtered b/w image.


  • CCDSoft, CCDStack, Photoshop CS w/ the Fits Liberator plugin. Noel Carboni's actions.

  • eXcalibrator for (b-v), (v-r) star color calibration, using 7 stars from the NOMAD1 database.

  • PixFix32 (pre-beta) to repair hot/cold pixels and column defects.

  • CCDStack to calibrate, register, normalize, data reject, combine the sub exposures.

  • PhotoShop for color combine &  on-linear stretching.


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

DWB-111, the Propeller Nebula, is an emission nebula in the constellation Cygnus. Astronomers seem to have more questions than answers, regarding this nebula. The origin of the peculiar structure is still completely unknown. The nebula's distance and source of excitation are also undetermined. DWB-111 mass is believed to be quite low, probably less than 50 solar masses. Obscuring dust is closely associated with the nebula, but seems to occur mostly in front of it.


These false color images were acquired with SII, Ha and OIII filters mapped to the RGB channels respectively. The colors of top image more closely follow the Hubble Palette, with the color channels pretty much stretched to equal levels.  The presence of sulfur, hydrogen and oxygen are clearly shown. Red indicates the presence sulfur, green hydrogen and blue oxygen. With no color manipulation, the image would be basically green, due to the dominance of hydrogen.


The lower image was further processed to produce the orange and blue colors, made popular by the Hubble Imaging Team.