M31 - The Great Galaxy in Andromeda

M31 is the famous Andromeda Galaxy. Other than our galaxy's close companions, the Large and Small Megellanic Clouds, it is our closest major galaxy. M31, along with our own Milky Way galaxy, the great spiral galaxy M33 and M31's small companion galaxies, M32 and M110 (seen here as fuzzy patches above and below M31) form what is known as our Local Group. At a distance of 2.9 million light years, it is the most distant object visible to the naked eye. Even so, it takes a keen eye and a dark night to spot it clearly. Skies must have been much clearer and darker in past ages, since M31 was known to the Persians as early as 905 AD. It also appears on a Dutch star map circa 1500 AD. It has an apparent diameter of 3 degrees...6 times the width of the full moon.

M31 is nearly twice the size of our Milky Way at 200,000 light years in diameter. However, with an estimated mass of 300 to 400 billion suns, it is not as dense as our galaxy.

Date/Location:    October 4, 2008     Griffin/Hunter Observatory    Bethune, SC
Instrument:    Canon 40D (modified) Digital SLR through Takahashi FS-102NSV w/0.75 focal reducer
Focal Ratio:   f/6
Guiding:    Auto through 10" Orion Newtonian w/ SBIG ST-402 on an AP-1200 mount
Conditions:    Visually clear - moderate humidity
Weather:    70 - 60 F, still
Exposure: 198 minutes @ ISO 800 (66 x 3 min exposures)
Filters:    Baader UV/IR block internal to camera
Processing:    Focused, captured, RAW conversions, frame calibrations, alignment, Digital Development with ImagesPlus v3.50a. Final tweaking with Photoshop CS2.

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