Open Star Clusters.
Telescope: Takahashi FCT-76
Location: Cedar Park, Texas, USA
Time: 9 pm – 11 pm
Sky Transparency: 8
Limiting Magnitude: ~ 4.5
Lunar Phase: First Quarter
Winter in the Northern Hemisphere is a great time of the year to view Open Star Clusters. The easiest way to locate these objects is to “surf” the Milky Way, where they reside in greater numbers. Since open clusters come in all shapes and sizes, each observer quickly finds favorites which show up best in their particular telescope. The following sample illustrates the advantages and limitations of my own small apo refractor under magnitude 4.5 suburban skies.
- M 52 – Through my Takahashi 7x50mm Finderscope, I notice a faint glow that makes me stop to take a closer look; turns out it’s M 52. Using the FCT-76, only a few individual stars are seen within a spherical glowing background. With averted vision, several more stars are revealed. Overall, a very uninspiring object at this aperture from my suburban location.
- NGC 7789 – This ancient cluster is nothing more than a faint fuzz in my refractor, which is one of the reasons I’ve been getting aperture fever. I’ll revisit it from a dark site.
- NGC 457 – The “E.T.” or “Owl” cluster is attractive in any telescope and around 20 stars can be viewed with my 3 inch. Towards the “shoulders” is a grouping of faint, misty stars that I know with more aperture makes this object more “cluster like.”
- M 103 – This small cluster shows 5-10 stars and a hazy glow of unresolved stars along the center. Like NGC 7789 above, my little scope only resolves M 103 on the better nights.
- NGC 663 – This is a fine cluster for small scopes and much better than M 103 [make sure to look for this one]. I see an elongated spherical distribution of about 20 stars with the background glow of more members.
- Stock 2 – At last, a cluster that doesn’t require eye squinting! Stock 2 is a nice non-Messier cluster, large and loose, with many faint stars visible which resemble a moth’s wings. A small double lies on its edge and a larger congregation of stars [possibly another cluster] borders it in the direction of NGC 663. I first saw this unidentified grouping about 2 years ago, but have never fully investigated whether this is an actual cluster in its own right. Use binoculars or a wide-field telescope to see it.
- NGC 869/884 – The Double Cluster reminds me of a flower on a stem because of the string of stars leading up to it from Stock 2. Of the two clusters, NGC 869 has more stars concentrated towards its center than NGC 884, and many stars lie all around both. Colorful stars abound. Whichever magnification used, there’s always something new to be appreciated here.
- M 34 – Another easy Messier open cluster for the aperture impaired amateur. For the most part it’s rather loose in stellar distribution with about 30 stars [of course, this could be the result of a small scope being unable to pick out the fainter members]. I sometimes wonder what I’m missing at the eyepiece by not having a larger optical instrument.
- M 36 – Of the three Messier clusters in Auriga, M 36 is the easiest to resolve in the FCT-76. I count around 25 white stars and more with averted vision. It’s also the cluster from which I jump off to view the other two.
- M 37 – This cluster shows few stars at low power, but many pop out at around 54x. The number of stars here is very high judging from the background glow of unresolved cluster members [under excellent seeing conditions], but on most nights under my suburban skies, M 37 elusively conceals its true nature.
- M 38 – I see stars here with more ease compared to M 37. M 38 lies in a nice field of stars and is the widest of the three Auriga Messier clusters. It also has a smaller companion cluster beside it [NGC 1907] that shows up fairly well.