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Astrophotography by Bob Franke

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NGC 6791

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

Click here to view the image without Zoomify (3390 x 2260 - 780 KB)




12.5" RCOS @  ~f/9 (2897 mm fl) 0.64 arcsec / pixel.  The Zoomify image scale is 0.64 to 2.89 arcsec / pixel.


Paramount ME


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

Acquisition Data

7/12/2011 to 7/17/2011 Chino Valley, AZ... with CCDAutoPilot3 & CCDSoft.  AOL guided


Lum 525 min (35 x 15 min, bin 1x1 (best of 44)

RGB 405 min (9 x 15 min each, bin 2x2)

Software & Processing

CCDSoft, CCDStack, Photoshop CS3, Noel Carboni's actions and Russell Croman's GradientXTerminator.

eXcalibrator for (u-g), (g-r) color calibration, using 57 stars from the SDSS-DR7 database.

PixFix32 (pre-beta) to repair column defects.

CCDStack to calibrate, register, normalize, data reject,  combine the sub exposures, Selective deconvolution and RGB combine.

PhotoShop for non-linear stretching and LRGB combine.


North is to the bottom.

NGC 6791 is an open star cluster in the Lyra constellation at a distance of about 13,300 light-years. It was discovered by Friedrich August Theodor Winnecke in 1853.

The above image shows the cluster's color as seen from Earth. Correcting for foreground galactic extinction makes most of the fainter stars white to very slightly blue.

Notes from
Astronomers have found the equivalent of three out-of-sync "clocks" in the ancient open star cluster NGC 6791. The dilemma may fundamentally challenge the way astronomers estimate cluster ages, researchers said.

Using NASA's Hubble Space Telescope to study the dimmest stars in the cluster, astronomers uncovered three different age groups. Two of the populations are burned-out stars called white dwarfs. One group of these low-wattage stellar remnants appears to be 6 billion years old, another appears to be 4 billion years old. The ages are out of sync with those of the cluster's normal stars, which are 8 billion years old.

Source: NASA, ESA, L. Bedin (STScI)
Click here for the full story