Rosette Nebula NGC 2237 in Monoceros
Comparison Images in the Literature
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.
- 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.
- Sky & Telescope, Volume 59(3), March 1980, p. 265. Photo by D. Healy using an 8-inch f/1.5 Schmidt camera.
- Sky & Telescope, Volume 61(4), April 1981, p. 287. This photograph belongs to the Mount Wilson and Palomar Observatories.
- Sky & Telescope, Volume 62(6), December 1981, p. 557. Photo using the 2-meter Schmidt camera at the Karl Schwarzschild Observatory.
- Sky & Telescope, Volume 69(2), February 1985, p. 181. Photo by Jim Riffle using a 12-inch f/5 Astromak Maksutov Cassegrain.
- Sky & Telescope, Volume 75(3), March 1988, pp. 248-249. Photo by Jim Riffle using a 12-inch f/5 Astromak Maksutov Cassegrain.
- Sky & Telescope, Volume 77(1), January 1989, p. 110. Photo by Hubert A. Entrop using an 8-inch f/5 reflector.
- 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.
- Sky & Telescope, Volume 83(3), March 1992, p. 266. Photo by Preston Scott Justis using a 10-inch f/6 reflector.
- Sky & Telescope, Volume 83(4), April 1992, p. 463. Photo by George Greaney using a 5-inch f/5.9 Takahashi refractor.
- 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.
- Sky & Telescope, Volume 93(1), January 1997, p. 39. Photo by David Hanon using an Astro-Physics 7-inch f/9 refractor.
- 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.
- Sky & Telescope, Volume 52(10), October 2024, p. 48. Photo by Chris Schur using a 10-inch f/3.9 Newtonian.
Logbook
- 6-inch f/2.2 Celestron Origin
- Date & Time: 28 Feb 2025, 8:35 pm
- Location: Kempt Shore, NS, CA, 45°N
- Sky: Partly cloudy
- Temp & Wind: -1°C, windy
- Moon Phase: New Moon (1%)
- Moonset: 7:04 pm
- Sunset: 6:03 pm
- Technical: 10-sec exposures, 2-hour integration, png file, no filter, line power
- Post-processing: Built-in photo editing tools on Samsung Galaxy S23 Ultra smartphone and MacBook Air
Open Cluster NGC 2244
NGC 2244 Open Cluster Membership
Many of the young stars near the centre of the Rosette Nebula were created by the surrounding gas and are now the sources that illuminate it. Although we know the open cluster NGC 2244 exists in that location, there are background and foreground stars that are not cluster members. Usually membership to such a cluster can be determined by distance, proper motion and spectral type. Membership to NGC 2244 was an important subject of research in the late 1970s and early 1980s because of its insight into stellar evolution.
The Case of 12 Monocerotis
The brightest star in the cluster is 12 Monocerotis (HD 46241), shown in this cropped Origin image. It has a visual magnitude of 5.830 and is a spectral type K0III according to Simbad data. It is interesting to note what Robert Burnham, Jr. wrote about this star.
"The brightest member, 12 Monocerotis, is a yellow giant of magnitude 5.85, of spectral type K0III. This star, however, must have an abnormally high luminosity (about 2500 suns) if it is at the same distance as the cluster; either it is a foreground object or the attribution to luminosity class III is very seriously in error. The normal luminosity of a type K0III star is about 30 times that of the Sun." From Burnham's Celestial Handbook: Volume Two, Dover Publications, Inc., New York, 1978, pp. 1196-1198.
In the book Stars and Clusters, Cecilia Payne-Gaposchkin, Harvard University Press, Cambridge, Massachusetts, 1979, a more pointed comment about the membership of 12 Monocerotis appeared in the caption for Figure 7.4 on page 100.
"NGC 2244. The brightest stars near the main sequence of this very young cluster are blue supergiants; probably the redder star, of luminosity class III, is not a member."
Since the late 1970s, 12 Monocerotis has been singled out as being a foreground star and not a member of the open cluster NGC 2244. Examples of this from Sky & Telescope magazine are found in the following issues:
- Volume 75(3), March 1988, p. 248.
- Volume 79(2), February 1990, p. 234.
- Volume 83(4), April 1992, p. 463.
- Volume 84(5), November 1992, p. 512.
- Volume 85(3), March 1993, p. 38.
- Volume 14(4), October 2022, p. 25.
Coming soon ...
So, which stars have a high probability of being members of NGC 2244? I will discuss this next.
In progress ...
In progress ...