Nightscapes & Deep Sky Colors

Astrophotography Brian A. Morganti

M3 - Globular Cluster

Canes Venatici


M3 was discovered by Charles Messier on May 3, 1764. It was his first original discovery, but he logged it as a nebulous object not to be confused with a comet. William Herschel was the first to resolve the cluster into stars, with a larger telescope, in 1784.  M3 is estimated to contain 500,000 stars, the brightest of which is magnitude 12.7. The 25 brightest stars have an average magnitude of about 14.  

M3, also catalogued as NGC5272,  is estimated to be 8 billion years old and is located roughly 34,000 light years from Earth.  It is nearly 180 light years in diameter. Many amateur astronomers consider M3 to be one of the finest northern globular clusters, followed only by Messier 13.  M3 has an apparent magnitude of 6.2, making it a very difficult naked eye target even with dark conditions. With a moderate-sized telescope, the cluster is fully defined.

North is to the right in the above image.


  • Date & Location:  May 13-14, 2015 - StarEffects Observatory - Bernville, PA

  • Weather:  Light Breeze, average temp of 50F

  • Sky Conditions:  Clear with Above Average Transparency. 

  • SQM-L: Average 20.51

  • Optics:  TeleVue NP101is Refractor with 1.5x extender 810mm @ f8.1

  • Filter:  Astronomic  EOS clip-in CLS-CCD (Light Pollution Suppression)

  • Mount:  AstroPhysics AP900GTO

  • Guiding:  SSAG - 5 seconds exposures - Good Graph.

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

  • Exposure:  14 x 5min ISO400  (total 70 min)

  • Calibration Frames:  Darks, Bias 50F - 10 Field Flats w/Alnitak Flat Man

  • Processing:    Images Plus 5.75a, PS CS6, NIK filter tools 

  • Comments:  Excellent sky conditions prevailed for imaging, but lost some focus sharpness due to rapid 5 degree temperature drop during this relatively short imaging session. 



Astrophotography  -  Nightscapes & Deep Sky Colors