M101 is a bright galaxy in Ursa Major, located 24 million light years from Earth. To find it, center your attention on Mizar, the middle star in the handle of the Big Dipper. Looking through your finder scope shift from Mizar to nearby Alcor, then two degrees farther east until you come to 81 Ursae Majoris, the westernmost member of a string of four 5th-magnitude stars.
Follow the string to 86 Ursae Majoris, marking the eastern tip. From there look to the north for three 7th-magnitude stars set in a right triangle. M101 lies just east of the midpoint along the triangle’s hypotenuse.
M101 is one of the easiest spirals to observe, as a 10-inch scope is all that is required to resolve the main arms and maybe even show a H II region. The galaxy contains no less than ten H II regions and stellar associations, seven of which are bright enough to have their own NGC numbers.
NGC 5447 is one of the most prominent of these and may be found 5 arcminutes southwest of the galaxy’s core. Use a nebula filter when observing M101, this helps to sort out the H II regions from the stellar associations.
Finder map – field width 15 degrees, stars to magnitude 10.5.