Nightscapes & Deep Sky Colors

Astrophotography Brian A. Morganti

M101 "Pinwheel Galaxy"

Ursa Major

75% crop resolution view of M101 below

Messier 101 is a classic type Sc, face-on, spiral galaxy in Ursa Major. It is located 25 million light-years away. Like M33, it is also often referred to as the Pinwheel Galaxy.

Numerous HII emission nebulae and star-forming regions in M101 are visible in this image.  Bright pink knots in the spiral arms are gigantic clouds of glowing hydrogen gas ionized by hot young stars in clusters that formed out of the gas.  An asymmetry can be seen in the spiral arms of M101 and is believed to be caused by a near collision with another galaxy. The interaction caused density waves in the spiral arms to be amplified, compressing the hydrogen gas, leading to bursts of star formation.

M101 is twice the size of the Milky Way at 170,000 light-years in diameter, with a mass of 100 billion suns.  At least 5  other galaxies can be found in the wide field image at the top of this page.  The largest being Spiral Galaxy NGC5474 in the lower right-hand corner, with the smallest being PGC49919 barely visible as a faint edge on Spiral Galaxy to the left of the bright blue star above M101.


  • Date & Location:  April 21/22 - 22/23 - /25th, 2015 - StarEffects Observatory - Bernville, PA

  • Weather:  Light Breeze to calm all nights. Temperature average 40F each image session.

  • Sky Conditions:  Clear transitioning to clouds all three nights.  Above average to average transparency.

  • SQM-L:  20:30 first night, 20:50 second night, 20:42 third night.

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

  • Filter:  Astronomik CLS (Light Pollution Suppression)

  • Mount:  AstroPhysics AP900GTO

  • Guiding:  Orion SSAG @5 seconds exposures.

  • Camera:  Canon T1i (500d) Hap Griffin modified - Baader UV/IR

  • Exposure:  23 - 10 minute subs  @ ISO1600 -  (230 minutes) 3 hours 50 minutes total exposure time.

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

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

  • Comments:  My first time imaging this target, also first time imaging with new custom white balance set with CLS filter in place in order to yield truer star and target color (no reddish cast as when CWB set without CLS filter in place).  


Astrophotography  -  Nightscapes & Deep Sky Colors