Messier 46 or M46, also known as NGC 2437, is an open cluster of stars in the slightly southern constellation of Puppis (lower left in the image). It was discovered by Charles Messier in 1771. Dreyer described it as “very bright, very rich, very large.” It is about 5,000 light-years away. There are an estimated 500 stars in the cluster with a combined mass of 453 M☉, and it is thought to be a mid-range estimate of 251.2 million years old. The cluster has a very broadest (tidal) radius of 37.8 ± 4.6 ly (11.6 ± 1.4 pc) and core radius of 8.5 ± 1.3 ly (2.6 ± 0.4 pc).[3] It has a greater spatial extent in infrared than in visible light, suggesting it is undergoing some mass segregation with the fainter (redder) stars migrating to a coma (tail) region. The fainter stars that extend out to the south and west may form a tidal tail due to a past interaction. The planetary nebula NGC 2438 appears to lie within the cluster near its northern edge (the faint almost rainbow array of colored smudge at the top-center of the image), but it is most likely unrelated since it does not share the cluster’s radial velocity. This makes for superimposed objects of interest, another instance perhaps being NGC 2818. On the other hand, the illuminating star of the bipolar Calabash Nebula shares the radial velocity and proper motion of Messier 46, and is at the same distance, so is a bona fide member of the open cluster. M46 is located close by to another open cluster, Messier 47. M46 is about a degree east of M47 in the sky, so the two fit well in a binocular or wide-angle telescope field.
Messier 47 (M47 or NGC 2422) is an open cluster (Right of center in the image), and was discovered by Giovanni Batista Hodierna before 1654 and in his then keynote work re-discovered by Charles Messier on 1771. It was also independently discovered by Caroline Herschel.
There is no cluster in the position indicated by Messier, which he expressed in terms of its right ascension and declination with respect to the star 2 Puppis. However, if the signs (+ and −) he wrote are swapped, the position matches. Until this equivalency was found, M47 was considered a lost Messier Object. This identification as the same thing (ad idem) only came in 1959 with a realization by Canadian astronomer T. F. Morris. M47 is centered about 1,600 light-years away and is about 78 million years old. The member stars have been measured down to about red dwarfs at apparent magnitude 19. There are around 500 members, the brightest being HD 60855, a magnitude 5.7 Be star. The cluster is dominated by hot class B main sequence and giant stars, but a noticeable colour contrast comes from its brightest red giants.

Telescope: Astro Physics 155EDF (TCC) f5.4
Mount: Astro Physics 1600GTO
Camera: FLI PL29050 / CFW2-7
Guider: Agena Starguide II / ZWO ASI178MM
Filters: Astrodon II 50mm LRGB

L: 48×5 mins = 240 mins, R: 24×5 mins = 120 mins, G: 24×5 mins = 120 mins, B: 24×5 mins = 120 mins

Total Imaging Time: 10h 00m

Data Imaged remotely over 5 nights during January 2023.
Imaged from Observatorio El Sauce, Chile, in partnership with Fred Espenak.
Data acquisition & Processing by David Churchill.

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