Another new month, only this one is special for us up north. It signals the beginnings of spring (and autumn for our southern friends) and hopefully we are nearing the end of some of our colder weather. For many it also means various things like Messier Marathons, the unofficial beginning of galaxy season, the beginning of daylight savings time, or perhaps gardening. Whatever your favorite thoughts of spring may be, hopefully you will take a few moments to read through this month’s objects and add those that grace your sky to your nightly outings. So get out there every chance you can and simply enjoy the wonders of the night sky.
Northern Celestial Hemisphere
Harrington 6 / 22 Leo Minoris Group (Leo Minor, asterism, size=43.0’):
This grouping of stars, while sometimes called the “Sailboat Cluster”, is simply a random line of sight collection of unrelated stars. Consisting of 8 primary stars, it is dominated by 22 Leo Minoris (mag 6.5) at its eastern end with the other stars of 7th to 9th magnitude. In binoculars this group looks like an upside down sailboat that is sailing westward, hence its nickname. It is also known as Harrington 6 (Phil Harrington) and the 22 LMi group. There is an actual open cluster in Cassiopeia (NGC 225) which also carries the nickname of the “Sailboat Cluster” and the two should not be confused. So raise your binoculars or small scopes its way and check out this curious little group of suns. You can locate it just over 7° northeast of Mu Leonis (in the head of Leo).
NGC 2841 (Ursa Major, spiral galaxy, mag=9.2, size=8.1’x3.5’, SBr=12.6):
Discovered by William Herschel in 1788, he called it “a brilliant nebula” in his notes. Often cited as one that Charles Messier missed, this bright galaxy (relatively speaking) is one of my personal favorites. Located almost 2° southwest of mag 3.2 Theta Ursae Majoris between a pair of field stars (8th and 11th mag), it presents a large elliptical disk that may display uneven brightness across its face. One may glimpse a very small but bright core within the disk. With careful study it might be possible to detect an abrupt cutoff of light along the eastern side due to intervening dust within the galaxy’s structure. This object makes a fine target for imagers, with lots of internal detail that may be teased out with proper processing.
NGC 3231 (Ursa Major, open cluster, mag=10.0, size=9.5’):
The big bear constellation is certainly not known for open clusters, and to be truthful, this one does not help much with that general impression. Other than the somewhat elusive planetary nebula, Messier 97, Ursa Major is indeed the domain of galaxies. But this obscure cluster, if in fact it is even a truly bound cluster, attempts to buck that trend, though feebly at best. Discovered by John Herschel in 1832, he noted it as "A cluster of 20 stars more or less, 10,11, and 12m, scattered over a space of 10' dia.” Coarse and not well detached, it contains two subgroups of stars separated by a small void of less stellar density. It is located nearly 6.5° northwest of mag 1.8 Alpha UMa (Dubhe), on the way to the well known galaxy pair of Messier 81 and 82 (which we will focus on next month). Sure this cluster is obscure and certainly not a showpiece, but I encourage both visual and imaging members to give it a few moments of your time.
Southern Celestial Hemisphere
IC 2391 (Vela, open cluster, mag=2.6 size=1.0°, class=II3p:
This large and scattered cluster popularly known as the Omicron Velorum Cluster, is easily found with the naked eye because of magnitude 3.6 Omicron Vel. It presents well in binoculars and small wide field scopes. First mentioned by the Persian astronomer Al-Sufi in his “Book of Stars” in 964 AD as a “nebulous star”, Nicolas-Louis de Lacaille was the first to resolve it as a star cluster with his ½ inch telescope from South Africa. He called it “a heap of stars.” Indeed with the naked eye it is a fuzzy patch in the sky and with 10x50 binoculars you can see that it is a cluster dominated by bright Omicron. This large and pretty coarse scatter of stars is easy to enjoy with modest aperture.
NGC 2818 (Pyxis, planetary nebula, mag=8.2, size=8.0’, SBr=12.5):
This planetary nebula, discovered by James Dunlop in 1826, appears to be swimming in a sea of stars much like the combination of Messier 46 and NGC 2438 we highlighted last month. In fact John Herschel observing it from South Africa made that same comparison in his notes. Though it has been generally believed that the planetary is in fact a part of the open star cluster (catalogued as Collinder 206 and Melotte 96), more recent studies seem to indicate it is a foreground object to the cluster – just like NGC 2438 is to M46. The nebula lies in the western portion of the faint cluster (12th magnitude and dimmer stars). Its appearance is elongated in a roughly north-south orientation, and may reveal some uneven surface brightness across its dimension. It is responsive to both narrow-band nebula and O-III line filters. Giving its juxtaposition with the open cluster, both often listed as NGC 2818, it should provide an interesting contrast for imagers. No use looking for its central star as it shines feebly at magnitude 19.4.
NGC 3195 (Chamaeleon, planetary nebula, mag=11.6, size=42.0”x30.0”, SBr=12.2):
We now travel to the deep southern constellation Chamaeleon. It is one of twelve constellations created near the end of the 16th century by Petrus Plancius. With no stars brighter than 4th magnitude it is a dimmer and somewhat obscure group, and is not known as a DSO gold mine. Its main deep treat is this planetary nebula at very nearly 82 south declination. Discovered by John Herschel in 1835 while using his father’s 18.7 inch reflector in South Africa, he described it as a "planetary nebula, pretty bright, not quite uniform in its light, having two brighter patches.” His comments hint at its dual-lobed appearance, clearly seen in deep images. In typical amateur scopes it may be dim visually, but using either a narrow-band nebula or O-III line filter will help boost its contrast. The dim central star is listed as 15th to 16th magnitude range depending on the cited source.
I now place this small collection of deep sky gems in your hands. I hope you are able to add them to your regular observing/imaging plans. Whether they are new to you or a familiar acquaintance, enjoy the time well spent in their pursuit and leisurely study. Be one with the sky, learn its beauty and wonder at it all.
Astro Sky 17.5 f/4.5 Dob || Apertura AD12 f/5 Dob || Zhumell Z10 f/4.9 Dob
ES AR127 f/6.5 & ED80 f/6 on Twilight-II || Apertura 6" f/5 Newtonian on Twilight-I
TV Ethos 100° 21mm, 13mm || ES 82° 24mm, 18mm || Vixen LVW 65° 22mm
Pentax XW 70° 10mm, 7mm, 5mm || barlows
DGM NPB Filter || Orion Ultra Block, O-III and Sky Glow Filters || Baader HaB Filter
Primary Field Atlases: Interstellarum and Uranometria All-Sky Edition
"Astronomers, we look into the past to see our future." (me)
"Seeing is in some respect an art, which must be learnt." (William Herschel)
"What we know is a drop, what we don't know is an ocean." (Sir Isaac Newton)
"The eternal silence of these infinite spaces frightens me...." (Blaise Pascal)
"No good deed goes unpunished." (various)
"I have become comfortably numb." (Roger Waters)