I still remember my first view of oc 2244 and the Rosette Nebula. It was late winter 1971, and I lived in Sudbury, Ontario. Sudbury is a very cold place in the winter, and observing usually did not resume until March. I was using a 40 mm refractor from K-Mart, with a table top tripod sitting on a tv table in my front yard, beneath a street light. At 15x I was blown away by what I saw! It was my first major object of the season, and my first ever in Monoceros. The cluster was surrounded by faint nebula and I could count several stars, recognizing the now-familiar rectangular pattern of the main cluster body. It was so cold that night I had difficulty focussing, but finally managed to get a superb view, one that has stayed with me all these years. Armed only with the tiny star maps included with Olcott's guide to the heavens, there was nothing else immediately nearby to see and I soon moved north to oc 2264.
Readers of this column know by now that I like to begin near a pre-selected object and explore the nearby vicinity for other objects of interest. After I have completed work on the main object, I enjoy sweeping the area immediately surrounding it. However, even careful sweeping with a 12" scope, which is usually undertaken at low power, can easily miss other less conspicuous gems. This article will search out other deep sky objects within very easy reach of oc 2244.
Readers of this column know by now that I like to begin near a pre-selected object and explore the nearby vicinity for other objects of interest. After I have completed work on the main object, I enjoy sweeping the area immediately surrounding it. However, even careful sweeping with a 12" scope, which is usually undertaken at low power, can easily miss other less conspicuous gems. This article will search out other deep sky objects within very easy reach of oc 2244.
Let me go astray for a moment and talk briefly about travelling. Some people like to try and see all of Europe in ten days, and book their trip of a lifetime accordingly. My own taste in travel is exactly opposite to this. I would rather center myself for ten days in a great city, such as London, Madrid, Copenhagen or Barcelona, exploring a much smaller area in detail and making short excursions out of the city to nearby sites of interest. Not surprisingly, this is also a preferred method for me of observing the sky. Find a major site or object, enjoy its richness with various eyepieces, filters, etc., and then see what else is nearby. Have you ever observed the Leo Triplet of galaxies? This is a stupendous site in a scope 8" or higher, worthy of many revisits. However, there are more than three galaxies of interest, if the neighbourhood is explored in a little more detail.
And now back to oc 2244. The cluster itself is wonderful (as we have already seen) even in a very small refractor. In a really dark sky it is visible to the naked eye! The emission nebula surrounding the cluster is visible in good binoculars (I am told) as well as small telescopes. In the 12" it is seen best with a nebula filter (not the cluster, which lies at the dark center). I see something that reminds me of high cirrus clouds, a mottled haze that deepens and thins as one sweeps the large circle surrounding the star cluster itself. The nebula is given several NGC numbers, including gn 2237, 2238, 2239, and 2246, each representing a different area of brightness, and the whole nebula takes up a vast area of sky (80' x 60', or over 1 degree). To me the brightest part is in the north, around 1 o'clock to the cluster.
Immediately surrounding the main cluster and nebula are no less than seven other open clusters, providing enough challenge and entertainment for an hour or more of star hop observing. On a cold March night it is a welcome project to see so much and not move the telescope all over the sky. This article assumes you are looking at Map 116 from Uranometria 2000, all sky edition. Five clusters are from the Collinder catalogue, one is from Dolidze, and one is from the NGC list. I will briefly discuss each one, moving clockwise on the map.
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| Uranometria 2000 (old edition), showing the Rosette Nebula in Monoceros and surrounding deep sky objects. |
Slightly north of 2244 and considerably preceding is oc Cr. 92. About one third the size of Cr 97, it still appears fairly large and scattered. However, this one has a denser knot of fainter stars that surround a star of 8.5 mag. As magnification increases more stars come out to play. The cluster seems medium rich but has many mostly faint members.
South from Collinder 92 is oc Do 22. Nearly erased by the bright star 8, look north preceding from that star. The cluster lies between it and a tiny group of stars that resembles a mini-Lyra configuration. The area in and around Do 22 is rich in stars and fun to sweep. Getting back to star 8 for a moment, it is a lovely double star all on its own (4.5-6.5/13"), which I see as ivory and lilac. A 12.5 mag. star can be seen 94" away.
Moving to the 8 o'clock position from, and much closer to, 2244 are two Collinder groups that share a border. Oc Cr 104 is the smaller of the two, though it is not small. A large field of relatively bright stars are interspersed with dense pockets of fainter ones. Sweep back and forth from it to 2244 for lovely star fields that are part of no cluster but sometimes just as lovely. Immediately south following 104, and overlapping it on one side is oc Cr 107. At 35' in size, it is larger than 2244! It contains two named variable stars (V731 and V 732), and the official star count of 30 only considers the brightest members. There are many more faint ones. I used several eyepieces here, from 43x up to 120x.
Moving to the 11 o'clock position from 2244 we come to oc 2252, one of my favourite clusters in this cluster-rich constellation. I have nick-named this one the "Star Trek" cluster, as to me it roughly outlines the insignia worn by Star Fleet members; at least it seems so at lower power. There are about a dozen brighter members, and too many fainter ones to sketch well. The central area looks like a little cloud puff at 60x in the 12", but resolves nicely as magnification increases. 100x and 150x gave fine views. Watch for two distinct lines of stars that meet at the apex.
Our final cluster is north following 2252, and is the largest of the entire group (45'). oc Cr 106 and the area surrounding it are wonderful for casual sweeping and getting lost among the stars. The cluster itself has many widely scattered bright stars, along with two areas of fairly intense fainter patches. The following end has one of these faint groups, and the north preceding end has another, near a brighter star. Also contained in the cluster is V640, called "Plaskett's Star." It is a binary system consisting of two giant stars, and is one of the most massive systems in the galaxy.
Monoceros is a rich constellation for telescope users. Eight neighbouring clusters, a very large nebula, and some very fine areas for casual sweeping at low power make for a rich visual experience. I hope you enjoy your visit to one small part of this amazing constellation!
Mapman
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