TheSkySearchers

kt4hx wrote: ↑Sat Apr 24, 2021 10:08 pm We have to remember that Messier's efforts were less than perfect, like those before him and those after him. He was in the process of attempting to verify various nebulae reported by previous observers, and in this case one erroneously documented by Johann Hevelius in the 17th century. What he found was this pair of stars that did not appear nebulous to him. But he accurately calculated its position and while not nebulous, for his efforts placed it in his catalogue as #40.

Here are his notes of the observation:

"The same night of October 24 to 25, 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 should have, in 1660, the right ascension 183d 32' 41", & the northern declination 60d 20' 33". I have found, by means of this position, two stars very near to each other & of equal brightness, about the 9th magnitude, placed at the beginning of the tail of Ursa Major: one has difficulty to distinguish them with an ordinary [nonachromatic] refractor of 6 feet [FL]. Here are their position: right ascension, 182 deg 45' 30", & 59 deg 23' 50" northern declination. There is reason to presume that Hevelius mistook these two stars for a nebula."

For this first published list of objects in 1774, "Catalogue des Nébuleuses & des amas d'Étoiles" (Catalog of Nebulae and Star Clusters), he seemed to attempt to present a seemingly logical number of objects (45), rather than 43. Thus he included 44 and 45, both of which were known since antiquity and he described in his notes as clusters of stars.