The month of June signifies the beginning of summer in the north and winter in the south. The richness of the Milky Way plane begins to take a more prominent place in the nightly sky, bringing its beauty and treasures to center stage as the northern summer and southern winter progress.
This edition will highlight three interesting and diverse objects from each celestial hemisphere for your consideration. I encourage all to add these to your observing sessions, whether you would be seeing them for the first time or paying them a return visit. As always, posting of your visual reports, sketches and images of these targets are encouraged here in this forum by starting a new thread in the “Submissions” sub-forum. Why not share your TSS Monthly DSO Challenge adventures here so we can all share and discuss your experience. All submissions are truly appreciated. With that, let’s get started for the month of June.
Northern Celestial Hemisphere:
Messier 5 / NGC 5904 (Serpens, globular cluster, mag=5.7, size=23.0’, class=5):
Discovered in 1702 by Gottfried Kirch, it was obviously also observed by Charles Messier (1764). One of the premier globular clusters in the sky, it is one of my personal favorites. Bright and large, it can, under the right conditions, be seen with the naked eye. Even in binoculars and small apertures it can be impressive. It shares similar attributes with the Great Hercules Cluster, M13, with a very similar visual magnitude and angular size, as well as both being a class 5 on the Shapley-Sawyer core concentration classification scale.
Personally I prefer Messier 5 visually, as to my eye it presents subtly better visually. Of course that is purely a personal preference that can be difficult to put into words, and is certainly not shared by everyone. So while M13 is not in this month’s challenge list, I encourage you to look at it as well (and I am sure you will!), and do a comparison between the two to see which you prefer.
NGC 6210 (Hercules, planetary nebula, mag=8.8, size=21.0”, SBr=6.3):
About 4° northeast of magnitude 2.8 Beta Herculis, between the upraised arms of the mythical strongman, is this bright and beautiful planetary nebula. This object has an interesting discovery history. Although it was first observed by Joseph LaLande in 1799, who recorded it in a star catalogue, he did not recognize it as non-stellar. So typically credit for the NGC object is given to Friedrich Wilhelm Struve, who recognized it as a planetary nebula in 1825 while hunting double stars nearby. In fact, be sure to check out the double Struve (Ʃ) 2094 about 17.5’ SSW of the nebula. This pair is pretty even at mag 6.9 and 7.0 with a tight separation of about 1.2”. A third component at magnitude 11.0 lies northwest of this pair at about 25” separation.
It is informally known as the Turtle Nebula because of its appearance in deep images which reveal jets of material flowing out through its outer shell. This planetary is bright and holds up to high magnification, provided seeing permits. The mag 12.6 central star is not strongly present visually, but can be seen with moderate to larger apertures under good seeing conditions. Moderate to larger apertures may also reveal some subtle outer shell detail, indicating a ring-like appearance. It is well known for its beautiful pale blue color, which is not difficult to see because of the object’s high surface brightness. Some observers may see it as more of a greenish-blue, depending upon how their eyes interpret the color they pick up. It also responds well to narrow-band nebula and O-III line filters, which may enhance internal structural detail. Regardless, it is a fine and beautiful object and well worth a visit whether you do visual observation, sketch or image.
Messier 102 / NGC 5866 (Draco, lenticular galaxy, mag=9.9, size=6.5’x3.1’, SBr=12.9):
The famous “Spindle Galaxy” is found just over the border from northeastern Bootes in the large and meandering Draco the dragon. It is known for its history of confusion almost as much as its beauty as an object. After much ado about the identify behind the 102nd entry in Messier’s list of objects, this lenticular is generally accepted as being the correct object, though not without some disagreement still. If Messier’s colleague Pierre Méchain did indeed discover NGC 5866 in 1781, he did so a full seven years before William Herschel, who is given discovery credit in some camps. Of course, since no one who was involved is around to validate these things, we can only try to interpret the notes they left behind to the best of our ability. In the end there will never be 100% agreement on discovery credit.
As indicated by its nickname, it presents a long and thin disk both visually and photographically. Its main details are an intensely bright core area, which in and of itself may appear as a small lens shape within the larger lens shape of the galactic disk. This central brightness is bisected by a thin dark lane that may or may not be seen visually. This depends on conditions, aperture and the observer’s experience. The galaxy extends away from the core, gradually thinning out to narrow tips. Sometimes in heavier light polluted areas where more subtle details can be lost to sky glow, the tips may appear blunter rather than smoothly transitioning to a thin. This object is full of mystery and intrigue, both in its identity and the beauty of its appearance.
Southern Celestial Hemisphere:
NGC 6025 (Triangulum Australe, open cluster, mag=5.1, size=15.0’, class=II2p):
At the northern edge of the southern triangle, snuggled up against the southern border of Norma, one can find this very pretty cluster. Discovered Nicolas-Louis de Lacaille in the 1751-52 timeframe, in his 8x ½ inch telescope he described it as "three faint stars in line in nebulosity." In reality there is no nebulosity associated with this cluster, and Lacaille was merely seeing light scatter from unresolved members.
The cluster field actually crosses into Norma a tiny bit, with the main body of the cluster firmly entrenched in TrA. It presents a split grouping separated by an area of less stellar density. The northern section is the richer of the two sub-groups, while a smaller boxier bunch lies in the southeastern quadrant of the cluster field. It is a curious and beautiful object that stands out well in a generally rich Milky Way field.
Messier 83 / NGC 5236 (Hydra, barred spiral galaxy, mag=7.5, size=12.9’x11.5’, SBr=12.7):
Here is another Nicolas-Louis de Lacaille discovery during his time in South Africa in the 1751-52 timeframe. In his small telescope he saw it as a “small, shapeless nebula.” This object has the distinction of being the only galaxy that Lacaille discovered. It was of course observed by Charles Messier (1781), who added it to his famous list of objects. It was also observed by other pioneers of early observational astronomy, such as William and John Herschel as well as James Dunlop. Its spiral nature was discovered in 1862 by William Lassell using a 48 inch reflector.
Colloquially known as the “Southern Pinwheel Galaxy”, at -29°51'56" declination it is the 8th most southern in Messier’s list, lying just 14.5’ north of the Hydra-Centaurus border. Though visible from the mid-northern latitudes, it is not well placed for the most advantageous observation for us up here. The closer one is to the equator or south of it, the better your views of the beautiful face-on spiral. It presents a large thick oval glow with a very bright concentrated core. When seen from darker locations where it achieves higher elevation one may catch a glimpse its delicate ghostly spiral structure.
NGC 5882 (Lupus, planetary nebula, mag=9.4, size=19.8”, SBr=6.7):
Deep into Lupus the wolf, nearly 1.5° southwest of magnitude 3.4 Epsilon Lupi this planetary presents a small glowing disk positioned within a curving line of four field stars ranging from 6th to 8th magnitude. Discovered by John Herschel in 1834, he described it as "a most elegant and delicate planetary nebula.” It was independently discovered by Williamina Fleming on a plate in 1894, this duplication went unchecked by Dreyer who bestowed the second identifier of IC 1108 upon the object, despite Herschel’s accurate position.
This small disk has been described as greenish to blue by some observers. Its magnitude 13.4 central star may be glimpsed with enough aperture, as may some weak internal structure. For most observers it may simply appear as a grayish rounded disk. Regardless, it stands as another testament to the violent and changing natural forces of our universe.
And there you have it for this month. Good luck in your pursuit and please let us know how you fared. It is through sharing of experiences that we can encourage and teach one another to become better at our craft. Until next time, keep looking up and enjoying the vast beauty of our universe.
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)