M 31 – The Andromeda Galaxy


M31 in the Messier Catalog is a spiral galaxy located 2.5 million light years from the Sun, in the constellation Andromeda. The Andromeda Galaxy is the closest spiral galaxy to the Milky Way and the largest member of the Local Group of sixty individual galaxies to which we belong. With a diameter of around 220,000 light years (ours is 100,000 ligh-years in size), it contains around a trillion stars, two to five times more than our galaxy.

With a visual magnitude of 3.4, the Andromeda galaxy is one of the few galaxies observable with the naked eye from Earth in the northern hemisphere. It is also one of the largest objects in the sky, with an apparent diameter of 3.18 °, more than six times the apparent diameter of the Moon observed from Earth. A pair of binoculars can help us locate it with more certainty while a small telescope reveals a wide oval spot. It is only through photography can we can reveal its spiral structure. This can be acomplished with a simple telephoto lens, with an exposure of at least 30 seconds. However, the camera and lens must be mounted on a motorized platform that follows the rotation of the Earth through a long exposure to avoid a blurry image.

Technical details:

Telescope: William Optics GT81 and 0.8x focal reducer
Camera: Canon EOS 6D Mark II
Exposure: 32 4-minute subs with ISO 1600
Place: Isle-aux-Coudres, Qc