M 40 is a bit of an oddball among Messier's objects. He was
searching this area, near where the Big Dipper's handle and
bowl come together, because a 17th century astronomer named
Johann Hevelius had reported some nebulosity in the area.
Messier did not see any nebulosity, but he did note the pair of
yellow stars close to the middle of this image, and he recorded
it as a double star. In reality, the two stars are probably not
a true double, but simply along nearly the same line of sight from
earth. One of them is about 750 light years away from earth, and
the other about 550 light years. There are, you will notice, several
galaxies in this area, including three spiral galaxies in a line
to the left of M 40, but Messier could not see any of these
dim objects with his telescopes.

Image Data:
Camera: Canon 350 XT (modified)
Exposure: ISO 800, 2 minutes x 32
Telescope: 10" Schmidt-Newtonian, Baader coma corrector