Here we can see clear evidence of the two 'populations' of stars identified over fifty years ago by the German-American astronomer Walter Baade. The oldest stars, which are billions of years old,  form the star clouds of Sagittarius in the southern Milky Way and are in orbit around the inner part of the Galaxy. They are cool and yellow and are the rich starry background here.  In the spiral arms are "clusters" of young, mainly blue stars, often still associated with the dust from which they formed. In this photograph we see one such young cluster, NGC 6520, which is in the foreground at a distance of about 7000 light years and spans about 10 light years in diameter.  These blue stars formed only millions of years ago unlike our sun which formed billions of years ago.

To the right (west) of the open star cluster is a dark nebula aka an absorption nebula and the molecular cloud Barnard 86, from which the stars of NGC 6520 surely formed. This nebula contains much opaque dust that blocks light from the many stars that would have been visible in the background.  On the opposite side of the nebula from the open star cluster, an orange/red (spectral class K4III. giant) star on the western edge of the dark nebula provides a 7th magnitude beacon to accent the view in superb fashion. Surrounding NGC 6520 & B86 is part of the tremendously dense starscape in the bulge of our Milky Way Galaxy---the extended halo of stars that surrounds the center of our Galaxy rendering the blackness of deep space beyond nearly invisible. 

IMAGE DETAILS:

• Date & Location:  August  4, 2013  - StarEffects Observatory, Bernville, PA

• Weather:  Calm, 60F/57Dp start - 57F/Dp55 end

• Sky Conditions:  Clear to Patchy Clouds with above average transparency. 

• SQM-L:  20:43 start - 20:49 end

• Optics:  TeleVue NP101is Refractor w/TeleVue Field Flattener = 540mm @ f5.4

• Filter:  IDAS-LPS 48mm (Light Pollution Suppression)

• Mount:  AP900GTO

• Guiding:  Orion SSAG @ 5 second exposures w/TeleVue TV60is

• Camera:  Canon T1i (500D) Hap Griffin Modified - Baader UV/IR & CWB

• Exposure:  35 min (10 x 3.5 minute subs) @ ISO 800 RAW

• Calibration Frames:  12-10min Darks, 12 Bias, 12 Field Flats w/Alnitak Flat Man - All Custom White Balance

• Processing:  Images Plus 4.50b, PS CS6, NIK filters

• Comments:   Image subs were kept short in duration in order to preserve the blue star colors of Open Cluster NGC 6520.  Wide field image at top is nearly full frame at 2 x 1.25 degrees.  Lower image was cropped and rotated at 75% resolution from the wide-field image.