Focal Pointe Observatory
Astrophotography by Bob Franke

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NGC 3521


Click the image for a larger size view. (1800 x 1200 - 966 KB)


12.5" RCOS @  ~f/9 (2880 mm fl) at 0.64 arcsec/pixel. Shown at 1.31 and 3.15 arcsec/pixel.


Paramount ME


SBIG STL-11000 w/ FW8 filter wheel, AstroDon Gen-2 Filters

Acquisition Data

3/23/2014 to 4/24/2014 Chino Valley, AZ... with CCDAutoPilot, CCD Commander & CCDSoft, AOL guided.


Lum  600 min. (20 x 30 min. bin 1x1)

Lum  180 min. (12 x 15 min. bin 1x1)

RGB  360 min. ( 8  x 15 min. bin 2x2, each)

Software & Processing Notes

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

  • eXcalibrator v4.25 for (g:r) color balancing, using 55 stars from the SDSS-DR9 database.

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

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

  • PixInsight processing includes gradient removal, initial non-linear stretching with HistogramTransformation and MaskedStretching and selective use of HDRMultiscaleTrans to enhance the detail in the center of the galaxy.

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

  • Noiseware 5, a PhotoShop plug-in.


North is to the right.

NGC 3521 is located in the constellation Leo. On the scale of cosmology, the galaxy is practically in our backyard at a distance of only 52 million light years. NGC 3521 is commonly known as the Bubble Galaxy. This is because of the galaxy's large shell, likely caused by a series of mergers with smaller satellite galaxies. Deep exposures reveal the tidal tail extending to the right. The shape of this tale could also prompt a common name of the Goldfish Galaxy.