Skies By Africa

Images of the Heavens By Eric Africa

M51, the Whirlpool Galaxy

M51 is a "classic" spiral galaxy. In fact, this is the archetype of the "spiral nebula", as it was the first "nebula" to be described as having a spiral shape by William Parsons, the Third Earl of Rosse, using a huge 72" reflector.

M51's distinct spiral shape is likely caused by encounters with its companion, NGC 5195. This shape also makes it one of the most photogenic galaxies in the northern sky, and it is one of the favorite targets of imagers. This shape has also earned it the nickname "The Whirlpool Galaxy".

M51 is fairly bright, though views of it from my backyard and an 8" telescope are pretty disappointing: only the cores of the two galaxies are faintly visible. With an 18" telescope at a dark site though, the galaxy looked like a black-and-white image. This galaxy is also what got me hooked on imaging. I was trying out an astronomy CCD camera (ST-7Ei) in my backyard back in 2003. I used that same 8" telescope that only showed faint blobs of the galaxies' cores. A ten-second exposure revealed the galaxy's spiral shape and arms. I was hooked on imaging right then and there.

The image on this page is my most recent attempt at this galaxy. This is one of the very first galaxies I tried shooting in earnest back in 2004. At 820mm focal length, this shot showed me that if I was to shoot galaxies at an image scale (very loosely defined: "magnification") that would satisfy me, I needed a longer focal length scope. That was when I tried a Celestron C8 as well as a Takahashi Mewlon 210. I shot M51 in 2005 with the Mewlon 210, though this was a brief shot mostly aimed at revealing a supernova in the galaxy. I tried again in 2009 , and this latest one is as of 2010. As you might surmise, this is one target that I keep coming back to again and again.
Constellation: Canes Venatici
When Visible: March - July
Distance: 37 Million Light-years
Date: March 2010
Location: New Mexico
Exposure Details:
L: 19 x 15 Minutes binned 1x1
R: 13 x 15 Minutes binned 1x1
G: 13 x 15 Minutes binned 1x1
B: 13 x 15 Minutes binned 1x1
Equipment Used: 10" RCOS Ritchey-Cretien on a Paramount ME. SBIG ST-10XME with 5-position filter wheel  and Astrodon HaLRGB filters. AO-8 adaptive optics unit. Guided using the camera's built-in guide chip and AO-8 unit.
Acquisition Software : MaximDL, TheSky6, ACP
Processing Software: MaximDL, Photoshop CS4, IrFanView, Noel Carboni Actions