Here we are with new skies and some new objects for you to add to your normal observing, sketching and/or imaging plans. As the months pass, our sky rotates bringing interesting objects into view. This constant change keeps things fresh and interesting, giving us an endless source of deep sky objects to pursue. This constant change also invites and challenges us to pursue our love of the night sky.
For this bi-monthly challenge, we northerners will take a peek into Cassiopeia, Lacerta and Cygnus. Our friends south of the equator will get to visit Octans, Aquarius, Sculptor and Grus. All these highlighted constellations of course contain far more treasure than we can cover here in any single issue. Certainly all are worthy of your attention beyond what is contained in this challenge. So once you are in each constellation, I encourage you to look around to see just what can be found.
So let’s delve into the objects for September and October. Be sure to check the list for the opposite celestial hemisphere. Depending upon your latitude, you just might be able to pick up something in the list that lies beyond the celestial equator. Good luck and as always, have fun. Please report your results so that we can all share in them and learn together.
Northern Celestial Hemisphere:
IC 1590 (Cassiopeia, open cluster, mag=7.4, size=4.0), type=III1m:
NGC 281 (Cassiopeia, bright nebula, mag=??, size=35.0’ x 30.0’):
This open cluster and emission nebula are a two for one deal. The cluster, IC 1590, is embedded in the heart of NGC 281 and is the primary energizer of the nebula. The duo are located about 1° 41’ due east of the bright star, mag 2.2 Alpha Cassiopeiae (Shedir). The cluster is a tight grouping at the center of its progenitor nebula, and is dominated by the quadruple star ADS 719, with the A through D components ranging from mag 7.8 to 9.7. With careful study one can see the small cluster swaddled in the misty hazy of the nebula, which is sometimes called the Pac Man Nebula based on its appearance in deep images. Some sources mistakenly list the nebula and cluster under the single identifier of NGC 281, but that is incorrect, as each has its own place in the NGC/IC Catalogue. Use of a narrow-band nebula filter, such as the DGM NPB or Orion Ultra Block can help with picking up the nebula visually by boosting its contrast. The pair is a fine target for imagers, providing a nice contrast between the two parts of the whole. Turn your scopes their way and see what you can make of this interesting combination.
Historically, the nebula NGC 281 was discovered by Edward Bernard in 1881, and possibly re-observed by Barnard in the 1890’s and unfortunately given a second identifier of IC 11. Credit for the embedded cluster, IC 1599, goes to Guillaume Bigourdan who was the first to bring it to our attention in 1899.
NGC 7209 (Lacerta, open cluster, mag=7.7, size=25.0’, class=III1p):
This nice open cluster is located in the celestial lizard, just inside its border from Cygnus. A William Herschel discovery in 1788, he described it as "a large cluster of pretty compressed considerable large [i.e. bright] stars, above 15' diameter."
The cluster offers a rich grouping of stars in an overall generally rich stellar field. Depending on conditions and aperture it is possible to see upwards of 30 to 40 stars scattered over its angular dimension, with numerous pairs and curves of stars being seen. Lacerta is an often overlooked constellation between Cygnus and Andromeda. But it does contain some nice open clusters and other types of DSOs to challenge the observer/imager, and this is a fine example.
NGC 6826 (Cygnus, planetary nebula, mag=8.8, size=27.0” x 24.0”, SBr=7.4):
The famous “blinking planetary” is located just under 1.5° ENE of mag 4.5 Theta Cygni. This object was discovered in 1793 by William Herschel. He described it in detail thusly - "a beautiful phenomenon. A bright point, little extended, like two points close to one another; as bright as a star of the 8-9 magnitude surrounded by a very bright milky nebulosity suddenly terminated, having the appearance of a planetary nebula with a lucid center. The border, however, is not very well defined. It is perfectly round and I suppose about 1/2' in diameter. It is of a middle species between the planetary nebula and nebulous stars."
The curious blinking effect that gave it the nickname is because of the bright central star of mag 10.4. When viewed with direct vision, the central star dominates the nebula’s disk, but with averted vision, the nebula takes prominence over the central star. However, with larger aperture, the increased brightness of the nebula’s disk mitigates this blinking appearance. Like most planetary nebulae, it responds well to an O-III line filter. In larger apertures some unevenness within its disk may become apparent, and one may glimpse some annular structure as well.
NGC 6946 (Cygnus, spiral galaxy, mag=8.8, size=11.5’x9.8’, SBr=13.8):
This face-on barred spiral straddles the Cepheus-Cygnus border. However, its center point lies just inside Cygnus, so that is where it calls home against the night sky. Famously known as the Fireworks Galaxy because it has experienced 10 observed supernovae over the past century, it was discovered by William Herschel in 1798. In his notes he described is as "considerably faint, very large, irregular figure, a sort of bright nucleus middle. The nebulosity extends 6 or 7'. The north seems to consist of some very small [i.e. dim] stars; the nebulosity is of the milky kind. It is a pretty object." It also appears in the Arp Catalogue of Peculiar Galaxies as Arp 29 being an example of a galaxy with one heavy arm.
Similar to most face-on oriented and large angularly sized galaxies, it appears fainter due to lower surface brightness. This object also lies near the primary Milky Way plane, thus it also suffers some obscuration by galactic dust within our galaxy. It presents delicate spiral structure, and lies between a spiral and barred spiral in morphology, with a small weak central bar. For many observers it will only appear as a thick oval diffuse ghostly glow in a fairly rich star field. But with more aperture and darker skies, its diaphanous spiral structure can be glimpsed.
Southern Celestial Hemisphere:
Melotte 227 (Octans, open cluster, mag=5.3, size=50.0’, class=II2p
Discovered by Philibert Jacques Melotte around 1915, this very deep southern object was looked upon as an open cluster initially. However, some studies have concluded it is merely a non-related line of sight asterism, though some sources still plot and list it as a cluster. Also known as Collider 411, it is located just over 4.5° southwest of magnitude 3.7 Nu Octantis. It is best viewed with lower magnification and a wider field. While the large field contains about 40 stars, one should be able to discern upwards of 15 members of magnitude 10 and brighter. At -79° declination, it is indeed a deep southern object. However, if it graces your sky, try pointing a smaller aperture wide field scope or even binoculars its way to see how many stars you can pick out.
NGC 7009 (Aquarius, planetary nebula, mag=8.0, size=34.8”, SBr=6.6):
One of the glorious objects below the celestial equator is the famous Saturn Nebula, located not quite 1.5° west of mag 4.5 Nu Aquarii. Discovered by William Herschel in 1787, he described it as "considerably bright, strong nebulosity of an irregular square figure.” The curious nickname, attributed to Lord Rosse, comes from the stubby extensions (ansae) that can sometimes be seen protruding from both sides of the slightly oval disk. This feature gives the vague illusory effect of edge-on rings.
Somewhat large for a planetary, its bright disk often appears as pale blue in color. With larger aperture and increasing magnification, one may glimpse some darker areas within the object’s envelope. The ansae themselves can be elusive and subtle in appearance. This is one of the brightest planetary nebulae in the sky and is a popular object for both visual observers and imagers as well. Being one of the few such objects in which observers are very likely to visually see color also makes it an attractive target in the night sky.
NGC 7507 (Sculptor, elliptical galaxy, mag=10.4, size=2.8’x2.7’, SBr=12.3):
NGC 7513 (Sculptor, barred spiral galaxy, mag=10.6, size=3.2’x2.1’, SBr=12.4):
These two galaxies in eastern Sculptor make a fine duo in the same field of view at only about 18’ apart. NGC 7507 lies southwest of NGC 7513, and is located not quite 3.5° northeast of mag 1.2 Fomalhaut (Alpha Piscis Austrini).
NGC 7507 will present a small round diffuse glow, as is typical for elliptical galaxies. Look for a small brighter core within the galactic disk. About 18’ to the northeast and within the same field of view you should pick up NGC 7513. Contrasting with the other galaxy in the view, this one presents a more elongated oval in the WSW orientation. It too is moderately bright for a galaxy and could likely reveal a small brighter core region within its disk. You should notice a wide pair of stars (mag 7.9 and 10.4) just south of the galaxy which adds to the curiousness of the view.
Interestingly both galaxies were not discovered by the same observer at the same time. Despite being relatively close together in the sky and of similar brightness, William Herschel discovered NGC 7507 in 1783 and Albert Marth discovered NGC 7513 in 1864. I find that a very curious little fact indeed.
IC 5148 (Grus, planetary nebula, mag=11.0, size=2.2’, SBr=12.4):
This is indeed a curious object, with its thicker annulus and smaller dark central “hole.” A mag 10.3 star (PPM 302060) sits just under 2’ SSW of the nebula’s center and helps identify the field. Using an O-III line or narrow-band nebula filter will improve the view of this object, and large apertures may reveal its dim mag 16.5 central star. It is fairly large for a planetary nebula and can have a ghostly appearance in the eyepiece with smaller apertures and without a filter. Larger apertures begin to reveal its true beauty. Just over 1° WNW of mag 4.5 Lambda Gruis, this dimmer planetary is sometimes referred to as the “Spare Tire Nebula” due to its thick annulus and dark center.
Discovered in 1894 by noted Australian amateur astronomer Walter Gale, it was assigned the identifier of IC 5150 by Dreyer. Then in 1897 it was independently discovered by Lewis Swift and given the secondary identifier of IC 5148 by Dreyer. Though normal protocol would dictate it be known by the identity assigned the original discovery (IC 5150), almost all sources utilize the secondary identifier of IC 5148. One has to wonder if this is because Swift was a professional astronomer, while Gale was a “mere” amateur. Both gave positions that were more or less equally inaccurate, but Gale’s description was spot on and thus he should be given credit and the assigned IC identity used as the primary. But unfortunately history is not always fair.
That is all for this time around. I hope you enjoy adding the above objects to your observing/imaging plans for September and October. Getting a little off the beaten path is a good way to challenge your observing skills and add some spice to your nightly sky searches. Good luck and let us know how it goes!
Scopes: Astro Sky 17.5 f/4.5 Dob || Apertura AD12 f/5 Dob || Zhumell Z10 f/4.9 Dob ||
ES AR127 f/6.5 || ES ED80 f/6 || Apertura 6" f/5 Newtonian
Mounts: ES Twilight-II and Twilight-I
EPs: AT 82° 28mm UWA || TV Ethos 100° 21mm and 13mm || Vixen LVW 65° 22mm ||
ES 82° 18mm || Pentax XW 70° 10mm, 7mm and 5mm || barlows
Filters (2 inch): DGM NPB || Orion Ultra Block, O-III and Sky Glow || Baader HaB
Primary Field Atlases: Uranometria All-Sky Edition and Interstellarum Deep Sky Atlas
"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)
"No good deed goes unpunished." (various)
“Some people without brains do an awful lot of talking, don't you think?” (Scarecrow, The Wonderful Wizard of Oz)