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Celestial Christmas Trees
Although its another 6 weeks till Christmas, you already can enjoy the view of three celestial Christmas trees around this time of the year: M 39 in Cygnus, M 103 in Cassiopeia and NGC 2264 in Monoceros. However, if you want to observe all three in one night, start early in the evening and stay up until way after midnight.

1. M 39 (NGC 7092)
At the end of October / the beginning of November Cygnus is high in the southwestern sky around 20.00 hours UT. You can find M 39 about 9 degrees to the east-northeast of Deneb, the bright star marking the tail of the Swan. Although M 39 fits in the 48’ field of view of my telescope 8-inch Klevtzov, I find that M 39 is at its best in my 15x80 binoculars (f.o.v. 3.5 degrees). With plenty of space surrounding the cluster, M 39 stands out nicely from the neighboring star fields and its triangular shape makes it look like ......... a Christmas tree. M 39 has a diameter of 31’ and visual magnitude of 4.6. In the 15x80 I see about 20 to 25 stars ranging from magnitude 7 to 10, a very pretty sight.

M 39 (image from SkyTools2 by CapellaSoft)

2. M 103 (NGC 581)
This open cluster in Cassiopeia is often overlooked because of the fact that it is very small and therefore not “spectacular”. M 103 can be located very easy. First find Ruchbah (Delta Cassiopeiae). Go 1 degree to the east-northeast. There you will find M 103. Until now I did not resolve this small open cluster completely with my 15x80 binoculars, but I definitely detected some stars superimposed on a somewhat hazy background of M 103. In the 8-inch Klevztov at 133x Messier 103 is resolved almost completely. M 103 has a diameter of 6’ and a visual magnitude of 7.4. With 25 to 30 stars ranging from magnitude 8 to 12, the triangular shape of M 103 definitely makes it look like another Christmas tree in the night sky. Three of the cluster’s brightest stars mark the tips of the triangle. When I increase the magnification I gradually detect more and more, fainter stars. The star at the "top" of the Christmas tree is yellow white. The star at the southeast apex is bright white. Others report a 9th magnitude red star at the centre of the cluster. Until now I haven’t “seen” it but maybe my telescopes aperture is to small to detect colours of 9th magnitude stars. Anyway, M 103 is a lovely small open cluster, so be sure to visit this celestial Christmas tree with your telescope the next time your in the Cassiopeia area.

M 103 (image from SkyTools2 by CapellaSoft)

3. NGC 2264 (The Christmas Tree Cluster)
The last of the three Christmas trees, NGC 2264, can be found in Monoceros. During this time of the year you have to wait until three o’clock in the morning to see the constellation culminate high in the south. NGC 2264 (nicknamed the Christmas Tree Cluster) is very easy to find. From 31 Xi Geminorum go south-southwest for about 3 degrees where you will find the 5th magnitude 15 Monocerotis, the brightest star of NGC 2264. In my 15x80 binoculars I already see almost all the stars that mark the outline of this heavenly Christmas tree. NGC 2264 is a large, bright open cluster with a diameter of 20’ and a visual magnitude of 3.9. In my 8-inch Klevtzov at 62x I see about 20 to 30 stars. When increasing the magnification I detect more and more fainter stars. By the way, in my Klevtzov-Cassegrain, the Christmas tree stands upside-down.

NGC 2264 (image from SkyTools2 by CapellaSoft)

Well, here ends my journey to the three celestial Christmas trees. I enjoyed it very much and I can only recommend these three open clusters wholeheartedly. Happy “tree” spotting!
Posted by Math on 11/07 at 01:26 PM
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