In the Messier catalogue of nebulae and clusters, as reprinted on the April 1966 issue, no description or position is given for M40, but a reference is provided to Owen Gingerich's statement of 1960 that this object is a pair of faint stars.
Which pair? Dr. Gingerich sent me this translation of Messier's original description, from Mémoires de l'Académie Royale des Sciences, 1771:
"The same night on October 24-25, [1764,] I searched for the nebula above the tail of the Great Bear, which is indicated in the book Figure of the Stars, second edition. Its position in 1660 was right ascension 183d 32' 41", declination 60d 20' 33". By means of this position, I found two stars very near each other and of equal brightness, about 9th magnitude, placed at the beginning of the tail of the Great Bear. One can hardly distinguish them in an ordinary (nonachromatic) refractor of 6 feet (length). Their position is 182 deg 45' 30", +59 deg 23' 50". We presume that Hevelius mistook these two stars for a nebula."
The latter position, precessed from 1765 to 1950, is 12h 20m.0, +58d 22', which agrees almost exactly with the double star Winnecke 4, magnitudes 9.0 and 9.3, separation 49 seconds of arc. This is an easy pair in my 4-inch refractor at 25x. It was discovered by A. Winnecke in 1863 at Pulkowo Observatory.
Clearly, M40 is identical with Winnecke 4. But the Hevelius object is the 5th-magnitude star 74 Ursae Majoris, more than one degree away, as reference to his star catalogue will show.
JOHN H. MALLAS
5115 E. Tomahawk Trail
Scottsdale, Ariz. 85251
Photo Credit: This image of M40 was obtained by Evered Kreimer in 1966.
Image Caption:: The field of M40, Winnecke 4, is the double star right of the center; the very bright star is 70 Ursae Majoris, magnitude 5.7; below this is the 13th magnitude galaxy NGC 4290. This is a 10-minute exposure by Evered Kreimer on June 13, 1966, with the cooled camera described on page 106 [in the same Sky & Telescope volume; it is also described in Mallas and Kreimer's Messier Album, p. 30].