|M31 "Andromeda Galaxy," M32 and M110: Galaxy Group (Andromeda) RA: 00h 42.7m / DEC: +41° 16'.1|
Instrument: 10-inch Starfinder
"How far can you see with your telescope?" is among the questions I often get from people. The brightest quasars can be seen with modest aperture across distances exceeding one thousand-million light-years. This is a mind boggling distance to most people. Admittedly, I have difficulty putting that distance in context. It's little more than an abstract concept to me. When I tell people the Andromeda Galaxy (M31) is visible to the naked eye at a distance of 2.4 million light-years, their jaws drop. The light from that familiar fuzzy patch of sky in Andromeda has taken more than two million years to get here. It left the galaxy long before modern humans walked the Earth.
M31 is a member of the Local Group, a gravitationally bound cluster of 35 galaxies that includes our very own Milky Way. The Andromeda Galaxy may be the largest member. If it's not, it is second only to the Milky Way Galaxy. M31 resides in Andromeda, 1.3 degrees west of 4.5 magnitude Nu Andromedae. M31 is easily visible to the naked eye from a dark site as a finger smudge against the starry sky. The galaxy stretches across three degrees of sky or the equivalent of six full Moons strung out in a line. I prefer the view through wide field instruments such as binoculars or a short focal length refractor.
My sketch displays the view through a 10-inch, f/4.5 Newtonian at 36X. The true field of view is about 90 arc minutes. M31 is visible as a swath of nebulosity cutting a path northeast to southwest through the field. It features a stellar nuclear region within a 15'x6' core. This is encased within the glow of more than 200 thousand-million stars appearing as a gauzy halo spilling beyond the boundaries of the eyepiece. M32, a satellite galaxy, is visible about 20' south of M31. M32 is a magnitude 8.0 elliptical galaxy, 4' in diameter, with a bright core. M110 is seen just inside the northern edge of the field. This elliptical galaxy covers a 15'x6' area and is the most difficult of the three to detect.
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Revised: February 10, 2002 [WDF]