Instrument

12.5" RCOS @  ~f/9 (2880 mm fl) at 1.28 arcsec / pixel.  Zoomify image scale is 1.71 to 3.42 arcsec / pixel.

Mount

Paramount ME

Camera

SBIG STL-11000 w/ internal filter wheel, AstroDon Gen-1 Filters

Acquisition Data

3/17/2010 to 3/19/2010 Chino Valley, AZ... with CCDAutoPilot3 & CCDSoft.

Exposure

Lum (no filter)   90 min. ( 6 x 15 min. bin 2x2)

R,G & B          225 min. ( 5 x 15 min. bin 2x2, each)

Software & Processing Notes

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

• eXcalibrator for (u-g), (g-r) color calibration, using 40 stars from the SDSS database.

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

• CCDStack to calibrate, register, normalize, data reject, combine the sub exposures, LRGB color, and luminance deconvolution.

• PhotoShop for  on-linear stretching.

Comment

North is to the top

Charles Messier discovered M48 in 1771. Charles mistakenly cataloged the cluster's location. This lead to later independent discoveries by Elert Bode in 1782 and Charles's sister, Caroline Herschel, in 1783. Charles published his sister's discovery in his catalog as H VI.22 on February 1, 1786.

The cluster spans roughly 23 light-years and lies about 1,500 to 2,000 light-years away, toward the constellation of Hydra. M48 is about 300 million years old, still young enough to have many young bright blue stars. Clusters, like this, are loosely bound by gravity. As they age, the clusters spread out and the member stars slowly escape.