Once known as the Great Andromeda Nebula, M31 is the dominant galaxy in the Local Group of galaxies that includes our own Milky Way galaxy. Typical of large spiral galaxies, M31 is believed to contain on the order of a trillion stars. At a comparatively close 2.5 million light years, the galaxy has the distinction of being the very farthest object we Earthlings can see with our naked eyes. At magnitude 3.4, the galaxy is easily visible from even modestly light polluted skies.

M31 has two dwarf elliptical satellite galaxies that are easily visible in this image. M32 is the small fuzzy patch just above the main galaxy, while M110 is the larger galaxy just below M31.

In this image, North is to the right. The image is cropped to 53% of the original frame.

Exposure Details
Lens	Canon EF 200mm f/2.8L II USM
Focal Length	200mm
Focal Ratio	f/3.5
Mount	Schaefer GEM - 7 1/2 inch Byers gear
Guiding	Piggybacked on C8, guided with an ONAG On-Axis Guider, Lodestar autoguider, PHD Guiding
Camera	Canon 450D - Gary Honis modified (Baader Mod)
Exposure	205 subexposures of 300 sec @ ISO 400 (17+ hours) plus 194 subexposures of 60 sec @ ISO 100 (3 1/4 hours)
Calibration	30 darks, 30 flats, 30 bias
Date	September 7, 8, and 9, 2013
Temperature	64F on 9/7, 65F on 9/8, 63F on 9/9
SQM Reading	21.40 (Bortle 4) on 9/7, 21.55 (Bortle 4) on 9/8 and 9/9
Seeing	4/5 on 9/7 and 9/8, 5/5 on 9/9
Location	Pine Mountain Club, California
Software Used	Images Plus 5.5 for camera control, calibration, stacking, digital development, advanced Lucy-Richardson deconvolution, multiresolution sharpening, star size and halo reduction, smoothing and noise reduction. Photoshop CS5 used for levels and curves, high pass filter, star shrinking, screen mask invert, unsharp mask, lab color, vibrance, select color, and match color. Gradient Xterminator for gradient removal. Carboni Tools for additional noise reduction and smoothing. Registar for image registration. Focus Magic for focus restoration. HLVG for additional color correction.
Notes	I'm very happy with how well the HDR combination came out in this image, as I was able to retain good details without blowing out the bright core. While the details in this image are fairly good, I was disappointed that I didn't capture good color in the many HII regions throughout the galaxy. I may try to add some Ha data to the image later on. This image was published in the Summer 2014 issue of Amateur Astronomy Magazine in my article entitled "Wide Field Astrophotography - Its Not Just For Beginners". This image won first place in Astrophotogallery.org's Hard-Galaxy category for November 2013.