M13 - Globular Cluster in Hercules


Copyright 2010 Hap Griffin

M13 is the best known of a class of objects called globular star clusters.  They are generally groups of several hundred thousand stars in a distinctly spherical shape that occupy a halo region around the central bulge of spiral galaxies, such as our own Milky Way galaxy.  They also are some of the oldest objects in the universe based on studies of the concentrations of elements within the constituent stars.  In the cores of such clusters, the stars are more than 500 times closer together than in normal space.

  M13 lies at a distance of 25,100 light years.  It is visible by the naked eye from dark sky locations as a very faint smudge along one edge of the "keystone" of stars in the central part of the constellation Hercules.  In 1974, M13 was selected to be the target of the first radio message to possible extraterrestrial civilizations intentionally beamed into space from the large radio telescope in Arecibo, Puerto Rico.


Date/Location:    February 13, 2010     Griffin/Hunter Observatory    Bethune, SC
Camera: QSI 583wsg
Filters: Astrodon E Series Generation 2 LRGB
CCD Temperature: -20 C
Instrument:    Planewave CDK 12.5"  
Focal Ratio:   f/8
Mount: AP-1200
Guiding:    Auto via the QSI camera's built in Off-Axis Guider mirror and a Starlight Express Lodestar Guider
Conditions:    Clear and cold
Weather:    21F, still
Exposure: 24 minutes total (8 x 1 minutes each in RGB binned 1x1)
Capture: CCDAutopilot 4 w/ Maxim DL Camera Control, focused automatically w/ FocusMax   
Processing:    Frame calibrations, alignment and stacking with ImagesPlus v3.80.  Finishing in Photoshop CS4.