Anyway, this month we shall be getting more into the northern winter and the southern summer, and all the various types of weather and conditions that those seasons entail.To start out the New Year we shall be taking the road a little less traveled. These objects for the most part are not frequently targeted by observers or imagers. Nonetheless, they are certainly most worthy of pursuit by those whose skies they grace.
For the northern contingent, we shall start with a three for one deal. Namely three overlapping open clusters in Taurus, and finish up with a challenging planetary nebula in Auriga. Our southern enthusiasts will have an eclectic mix of a fine summer (winter for the north) globular, a bit of an obscure open cluster (or perhaps asterism) in Pictor and finish up with a planetary nebula in Lepus. That is our lineup for January, and I hope you are able to add some of these to your observing or imaging plans. Good luck and please report your results here so we can share in your endeavors under the glorious night sky.
Northern Celestial Hemisphere
NGC 1746 (Taurus, open cluster, mag=6.1, size=42.0’):
NGC 1750 (Taurus, open cluster, mag=6.9, size=20.0’):
NGC 1758 (Taurus, open cluster, mag=8.7, size=9.0’):
This triplet of open clusters can be a confusing field to say the least. What would eventually be listed as NGC 1750 and 1758 were discovered by William Herschel in 1785. However, though in the same field of view, what would become catalogued as NGC 1746 is credited to Henrich d’Arrest in 1863, though it would seem obvious that Herschel also saw this grouping, though he did not discern it as separate.
The large field of NGC 1746 is a rich stellar patch of sky. Generally a scattered grouping ranging from 7th to 13th magnitude, it does contain a few clumpy areas. The field of NGC 1750, which is centered south of the center of NGC 1746, is one of these areas of slightly more stellar density which William Herschel discerned. Another one is NGC 1758, immediately northeast of NGC 1750 and east of the center of NGC 1746. Though all three clusters overlap, they are not related in any manner, being of varying distances.
There can be some disagreement about whether there are indeed three clusters here or two, depending upon the source. The general consensus is that NGC 1750 and NGC 1758 are the only clusters in this field, while NGC 1746 may be either a duplicate observation of NGC 1750 or just a clump of stars associated with that cluster. All I can add to this discussion/disagreement is that my own visual impression of the field was that of three distinct objects. One large and scattered, with two smaller ones of more compressed character involved within the larger cluster’s field. Nonetheless, give them a try to see if you can discern three distinct objects.
IC 2149 (Auriga, planetary nebula, mag=10.6, size=15.0”x10.0”, SBr=6.9):
This planetary is located about 1° 17’ NNW of bright Beta Aurigae (Menkalinan), which is an easily split double of mag 1.9 and 10.1 separated by about 3.11’ at a position angle of 42°. It was discovered in 1906 by Williamina Fleming on a prism plate captured at Harvard University.
The planetary may appear initially as a slightly fuzzy star, as its central star can overwhelm the small nebulous disk. Though the nebula has a higher surface brightness, the involved star does impact its visibility. The use of an O-III filter line filter can certainly tame some of the brightness of the star while boosting the visual contrast of the nebula. Visually it should appear as a very small whitish and slightly out of round object enveloping the central star. Not a robustly visible object, but certainly an intriguing little thing to add to your observing/imaging plans.
Southern Celestial Hemisphere
NGC 1851 (Columba, globular cluster, mag=7.1, size=12.0’, class=2):
This beautiful globular cluster is one of very few in the sky this time of year, making it a special treat. Visible for many mid-northern observers low in their southern sky, it is more of a prime time object for those closer to and south of the equator. This object was discovered by James Dunlop in 1826, and was also observed by John Herschel in 1835 during his time in South Africa. Herschel described it as a "superb globular cluster; very suddenly much brighter in the middle to a blaze or nucleus of light.”
Found not quite 6° southwest of mag 3.9 Epsilon Columbae, it sites just under 2° east of the Columba-Caelum border. Visually, with smaller apertures it can appear as a small and bright compact ball of light. Its core can be glimpsed as a pretty small intense brightness in the center of its disk. Its core is very compressed and intense as aperture and magnification increases. Resolution of member stars can be challenging though with larger aperture some very modest resolution may be glimpsed. Overall it is a bright and readily apparent object in an otherwise frequently overlooked constellation.
NGC 2132 (Pictor, open cluster, mag=8.0, size=45.0’):
The deep southern constellation of Pictor, depicting a painter’s easel, is home to this more obscure open cluster. It is frequently listed as an asterism or random line of sight grouping of stars rather than a true cluster. Discovered in 1836 by John Herschel while in South Africa, it is located almost 4° SSE of mag 4.5 Gamma Pictoris near the border with Dorado.
Visually it is a larger scattering of stars that is not particularly rich or overly detached from the general field. Its most obvious stars are a north-south zig-zag of four stars ranging in magnitude of 7.2 to 8.5. The remainder of its field is a non-cohesive spray of 9th to 11th mag stars.
IC 418 (Lepus, planetary nebula, mag=9.0, size=14.0”x11.0”, SBr=5.3):
This planetary is located about 2° ENE of mag 4.3 Lambda Leporis is the northern part of the celestial bunny. Initially it will likely appear as a fuzzy star, as its mag 10.2 central star will dominate its appearance. As one increases magnification and of course aperture, you will resolve a small but well defined whitish disk surrounding the star. It handles higher magnifications well because of its surface brightness. With larger apertures one may noticed a “blinking” effect, whereby staring right at the central star will reduce the presence of the surrounding shell, while averted vision will bring out the nebulosity more. This object is a low excitation planetary therefore utilizing a Hydrogen-Beta filter can yield good results in boosting contrast of the disk while reducing the presence of the central star. I’ve seen reports by users with apertures of around 18 inches and larger that there may be some reddish tones to the planetary disk.
This object was discovered by Williamina Fleming who noticed it on an objective-spectrum plate taken in 1891 at one of Harvard’s southern observatories. W.W. Campbell is credited with the first visual observation of the object, also in 1891. In his case, he was utilizing the 36 inch telescope at Lick Observatory and noted it as a very bright object with a blue coloration.
That is it for this month my friends. I hope you find these objects a curious change to the normal fare which most folks pursue this time of year. With the exception of NGC 1851, these objects may not be on most folk’s hit lists for night sky cruising. I hope you will give those that grace your local sky a look to see what you can make of them. Have fun and I look forward to hearing of your results.
And I never expected to bring you into the OC camp! But that said, I am very glad you are seeing them in a new light Graeme. Agree with Andrey, your image captures the essence of this triplet. Of course they are not flashy like some more prominent clusters, but they have a character all their own. Well done!
