Rosette Nebula NGC 2237 in Monoceros

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There are many Rosette Nebula images to be found online and in print, captured with several types of telescopes and cameras, then post-processed using techniques often not discussed. For comparison purposes, I prefer photographs in the printed literature because they have to pass an editorial review at some level in order to be accepted for publication. Here are some references from my home library.

1. Burnham's Celestial Handbook: Volume Two, Robert Burnham, Jr., Dover Publications, Inc., New York, 1978, p. 1197. Photograph taken with the Palomar Observatory 48-inch telescope.
2. Sky & Telescope, Volume 59(3), March 1980, p. 265. Photo by D. Healy using an 8-inch f/1.5 Schmidt camera.
3. Sky & Telescope, Volume 61(4), April 1981, p. 287. This photograph belongs to the Mount Wilson and Palomar Observatories.
4. Sky & Telescope, Volume 62(6), December 1981, p. 557. Photo using the 2-meter Schmidt camera at the Karl Schwarzschild Observatory.
5. Sky & Telescope, Volume 69(2), February 1985, p. 181. Photo by Jim Riffle using a 12-inch f/5 Astromak Maksutov Cassegrain.
6. Sky & Telescope, Volume 75(3), March 1988, pp. 248-249. Photo by Jim Riffle using a 12-inch f/5 Astromak Maksutov Cassegrain.
7. Sky & Telescope, Volume 77(1), January 1989, p. 110. Photo by Hubert A. Entrop using an 8-inch f/5 reflector.
8. Sky & Telescope, Volume 79(2), February 1990, p. 234. Photo by Tony Dallas and Daphne Mount using a 10-inch f/6.6 Newtonian reflector.
9. Sky & Telescope, Volume 83(3), March 1992, p. 266. Photo by Preston Scott Justis using a 10-inch f/6 reflector.
10. Sky & Telescope, Volume 83(4), April 1992, p. 463. Photo by George Greaney using a 5-inch f/5.9 Takahashi refractor.
11. Sky & Telescope, Volume 84(5), November 1992, p.512. Photo by Tony Dallas and Daphne Mount using an Astro-Physics 6-inch f/7.3 refractor.
12. Sky & Telescope, Volume 93(1), January 1997, p. 39. Photo by David Hanon using an Astro-Physics 7-inch f/9 refractor.
13. Deep Sky Objects, David H. Levy, Prometheus Books, Amherst, New York, 2005, p. 105. Photo by Dean Koenig using a 4-inch Astro-Physics refractor.
14. Sky & Telescope, Volume 52(10), October 2024, p. 48. Photo by Chris Schur using a 10-inch f/3.9 Newtonian.

To determine which stars belong to the open cluster NGC 2244 we have to turn to the scholarly literature. Two research papers are sufficient to allow me to label several high probability cluster members on my unprocessed Origin image shown here (note that the nebula regions are not as bright as the previous images).

1. UBV Photometry of NGC 2244, K. Ogura and K. Ishida, Publ. Astron. Soc. Japan 33, 149-176 (1981).
2. Membership of the Rosette Nebula Cluster, NGC 2244,L.A. Marschall, W.F. van Altena, and L-T. G. Chiu, The Astronomical Journal, 87(11), 1497-1506 (1982).

Reference 1 uses UBV photoelectric and photographic photometry to analyze 400 stars, mostly in the central region of the nebula. Only stars brighter than visual magnitude 14 were considered. Since Celestron Origin can resolve stars fainter than magnitude 20, all of the stars in this study are visible in this image provided they fall within the boundaries of the 1.27° x 0.85° field of view. The authors identified 164 likely cluster members. Rather than label all of these stars, I decided to reduce the selection by correlating these stars with the most probable members determined by the proper motion study in Reference 2.

Marschall et al. used the same 400 stars from Reference 1 and added two more. Their NGC 2244 data were taken from analysis of the Yerkes 40-inch and Allegheny 30-inch refractor plates spanning a 60-year time period from 1914 to 1974. The limiting magnitudes of these plates (18 exposures) ranged from 12.0 to 14.5. In total, relative proper motions were estimated for 287 of the 402 stars in this study. In order to reduce the number of cluster members from 164 for labelling purposes, I arbitrarily chose the stars from the 164 in Reference 1 that also had kinematic-based probabilities greater than 80% from Reference 2. Consequently, I have labelled 49 highly probable members using yellow labels/arrows. I also identified these stars using the Aladin Sky Atlas.

It is noteworthy that three prominent stars labelled in red have been determined to be foreground stars including 12 Monocerotis.

1. HD 46180, SB variable, V 8.61 (Type A3V)
2. HD 46107, V 8.75 (Type A1V)
3. HD 46241 (12 Mon), variable, V 5.83 (K0III)