Faint galaxies at magnitude 23.5 are easily visible... with the faintest found dimmer than 24. Within the entire field of view, there are about 3,890 NED cataloged galaxies at magnitude 23.5 or brighter. Essentially, every faint background smudge is a galaxy. 

Instrument

12.5" RCOS @  ~f/9 (2880 mm fl) at 0.64 arcsec / pixel.  Shown at 1.28 and 3.42 arcsec / pixel.

Mount

Paramount ME

Camera

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

Acquisition Data

6/17/2013 to 8/16/2013 Chino Valley, AZ... with CCDAutoPilot5 & CCDSoft AOL guided.

Exposure

Lum  870 min. (29 x 30 min. bin 1x1)

RGB  270 min. (  3 x 30 min. bin 1x1, each)

Software & Processing Notes

• CCDSoft, CCDStack, Photoshop CS6, PixInsight and Noel Carboni's actions.

• eXcalibrator v4.1 for (g:r) color balancing, using 70 stars from the SDSS-DR9 database.

• CCDBand-Aid to repair Kodak KAI-11000M vertical bars.

• CCDStack to calibrate, register, normalize, data reject, combine the sub exposures and create the RGB image.

• PixInsight for gradient removal and initial non-linear stretching.

• PhotoShop for the LRGB combine & final touch-up.

• Noiseware 5, a PhotoShop plug-in.

Comment

North is to the top.

Abell 39 is low surface brightness planetary nebula in the constellation of Hercules and at a distance of about 6,800 light-years. The nebula is unique in that it has a nearly spherical shell, with a radius of about 2.5 light-years. Another unique feature is that, for some unknown reason, the central star is slightly off center by 0.1 light-years. The image also shows the seldom seen surrounding interstellar cirrus.