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Stephen James O'Meara's Secret Sky: Deep naked-eye diving

April 2010: See if you can spot objects millions of light-years away with your eyes alone.
April 2010 M81
M81 in Ursa Major lies some 12 million light-years away, but is still faintly visible to the naked eye. The author estimates its magnitude at 6.9, and from mid-northern latitudes M81 sits high in the north during evening hours this time of year.
N.A. Sharp (NOAO/AURA/NSF)
In the November 2009 issue of Astronomy, I challenged observers to detect three naked-eye galaxies: Messier 31 (M31) in Andromeda, M33 in Triangulum, and NGC 253 in Sculptor. These island universes lie 2.9, 3.0, and 10.0 million light-years distant, respectively.

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