Winter's Mighty Hunter: Look to Orion, the embodiment of the season's night sky, to discover a diverse collection of celestial wonders.
Whose starry dagger nightly gleams My casement-lattice through
--Anonymous, Babylon, 1837
The glory of Orion, the Hunter, holds sway over winter nights with its unequaled brilliance. Our centerfold's all-sky chart depicts its attention-grabbing belt stars in a straight line straddling the celestial equator. Gleaming below his belt, Orion's starry dagger bears his foremost treasure, the Orion Nebula, an extensive tangle of nebulosity with a heart of sparkling gems.
The Orion Nebula (M42 and M43) is enchanting in any telescope, and the view through a large scope can never be forgotten. Georgia amateur David C. Riddle made the stunning sketch of M42 (shown far right) with his 18-inch reflector at 450x. It took five hours just to capture the tremendous amount of detail exposed in the bright region that frames the trapezoidal knot of four stars known as the Trapezium. It's truly a picture worth a thousand words.
Orion's dagger (or sword) is a wonderful sight through 15x45 image-stabilized binoculars. M42's graceful fan of lambent light wears three of the Trapezium's stars plus two more nearby. A dark notch named the Fish's Mouth juts in toward the Trapezium from the east-northeast. Petite M43 is punctuated by a single star. North of M43, a diaphanous, east-west nebula about 15' long embraces one faint and two bright stars. It marks the site of the nebula-cluster complex NGC 1973, NGC 1975, and NGC 1977. Above the complex, 13 stars of magnitudes 6 through 9 form the loose cluster NGC 1981 and charmingly trace out the path of a bouncing ball dribbled east-west for 25'.
Beyond the dagger, let's focus on the beautiful multiple star Sigma (a) Orionis, visible to the unaided eye as a single point near Zeta ([zeta]) Orionis (Alnitak), the leftmost star of Orion's Belt. A magnification of 87x in my 105-mm refractor reveals four components arranged in a slightly wavy line, all dressed in shades of white to blue-white. The brightest member comprises two stars that are too close together to distinguish through a backyard scope. They're tightly wedded by their mutual gravity, but the visible companions are only loosely bound to the system and may go their separate ways in the distant future.
Orion's belt stars are part of the impressive star cluster Collinder 70, a remarkable group so large that it's best appreciated through binoculars. Swedish astronomer Per Collinder called it "a very fine cluster" and assigned it a size of 250' x 120' in his 1931 catalog of star clusters. More than 100 stars show in the 15x45 binoculars. A particularly prominent S-shaped curve of fairly bright stars wends its way across the cluster between Alnilam and Mintaka, Orion's middle and rightmost belt stars. The belt stars are blue-white beauties, and two of the brightest non-belt stars blaze orange.
Off the southwestern side of Collinder 70, the naked-eye star Eta ([eta]) Orionis is a nice double to attempt splitting during good seeing (atmospheric steadiness). The 3.6-magnitude primary guards a 4.9-magnitude companion just 1.8" to the east-northeast. Through the 105-mm refractor at 127x, both are bluish-white, but there's more to the primary than meets the eye. Its spectrum shows that it's really composed of three stars in tight embrace.
Training the 15x45 binoculars on a patch of sky 2.5[degrees] northeast of Alnitak brings two reflection nebulae into view. Messier 78 is an obvious roundish glow with one barely seen star, accompanied by dimmer NGC 2071, which hosts a brighter star. Two stars adorn M78 in the refractor at 47x, looking amusingly like the eyes of a little ghost. Sweeping the scope 57' west takes me to the colorful double Struve 782. Its nearly matched, yellow-orange suns are far enough apart to separate at 28x. Shifting 1.8[degrees] east from M78 takes the scope to the open cluster NGC 2112, a granular haze at 17x and a pretty dusting of faint stars at 127x.
I recently observed NGC 2112 through Justin Cash's 8-inch reflector while in North Carolina. The cluster is readily visible at 35x as a small concentration of several faint stars. At 174x about 20 stars are loosely scattered across 9 1/2', the brightest one an orange ember at the cluster's northwestern edge.
NGC 2112 lies within a 2[degrees]-length of Barnard's Loop visible with 15x45 binoculars from Florida's Lower Keys. In the 105-mm scope at 17x with the help of a hydrogen-beta filter, I followed the nebula's unevenly bright curve for roughly 9[degrees], displaying a mean width of about 40'.
Next up is the planetary nebula Jonckheere 320, located 2.7[degrees] east-northeast of [Pi.sup.1] ([[pi].sup.1]) Orionis in Orion's shield. J320 is visible in my 4.1-inch refractor even at 28x, but it looks like a star. At 127x it becomes a tiny disk. Through the 10-inch scope at 115x, the nebula takes on a bluish cast, and at 299x it turns into a small oval that's brighter at its east-southeastern end.
In 1911 Robert Jonckheere cataloged J320 as a pair of 9.8-magnitude stars 2.17" apart. Five years later he wrote, "While observing with the 28-inch equatorial on January 22,1 noticed that the object that I have catalogued as J320 is not a double star, but... it appears with the larger instrument to be an extremely small bright elongated nebula" (The Observatory, March 1916).
From the shield, we'll move into Orion's upraised arm, where the open-cluster pair NGC 2194 and Skiff J0614+12.9 rests 1.5[degrees] south-southeast of Xi ([xi]) Orionis. The duo shows nicely in the field of the 10-inch scope at 70x, both speckled with very faint stars. On closer examination at 171x, NGC 2194 boasts 40 stars, many in a boxy, 5' core with a grainy backdrop. Its scraggly 8' halo is fertile in some places and barren in others. The Skiff cluster sports about half as many stars confined to 5'.
In northernmost Orion, we'll call on the emission nebula NGC 2175, 1.4[degrees] east-northeast of [Chi.sup.2] ([chi square]) Orionis. It's even visible through my 9x50 finder as a sizable glow around a star. At 68x in the 10-inch reflector, it's subtle. Adding a narrowband filter, NGC 2175 is a beautiful sight, softly glowing like backlit frost on the window of the sky. Its 25' spread is threaded with dark lanes and spangled with meandering chains and lines of stars. The nebula's northern border is particularly irregular. Just 3' east-northeast of the nebula's central star, there's a fairly small brighter patch harboring a star of its own. A little cluster sometimes cataloged as NGC 2175.1 resides at the nebula's east-northeastern edge. A filterless view at 115x shows 15 stars in a north-south, 4 1/2' x 3' group that includes a close double.
Our final fare is another cluster found by Arizona astronomer Brian Skiff. Skiff J0619+18.5 sits 1.2[degrees] east-southeast of 71 Orionis and consists of three clumps of stars. My 10-inch scope at 68x shows two of them forming a 13' triangular aggregation of about 35 stars, 9th magnitude and fainter. The denser clump forms the triangle's southern point, and the looser one to the north fashions its base. A detached group to the southwest contains the golden, 8thmagnitude star HD 254874. Altogether the cluster shows at least 60 stars in an irregular gathering whose maximum diameter is roughly 20'.
Orion harbors a wealth of deep-sky objects, from the spectacular, to the challenging, to the virtually unknown. Which appeal to you?
* Contributing Editor SUE FRENCH enjoys tracking down lesser-known sights in otherwise familiar skies.
Caption: David Riddle drew this deep view of the Orion Nebula over a stretch of several evenings. It took 5 hours at his 18-inch reflector at 450x to capture just the area surrounding the four bright stars that make up the Trapezium cluster.
Caption: William Herschel discovered the open star cluster NGC 2194 in 1784; but Skiff J0614+12.9 is a much more recent discovery. Brian Skiff (Lowell Observatory) found the latter with a 25-cm reflector around 1975 and reported It in the Observing Handbook and Catalogue of Defep-Sky Objects (Luginbuhl and Skiff) in 1989.
Objects in Orion Object Type Mag(v) M42/M43 Emission/reflection nebula 3.0 NGC 1973/75/77 Nebula/cluster complex 6.3 (nebula) NGC 1981 Open cluster 4.2 Sigma ([sigma]) Multiple star 3.8, 8.8, 6.6, 6.3 Orionis Collinder 70 Open cluster 0.6 Eta ([eta]) Double star 3.6, 4.9 Orionis Messier 78 Reflection nebula 8.3 NGC 2071 Reflection nebula -- Struve 782 Double star 8.6, 8.8 ([SIGMA]782) NGC 2112 Open cluster 9.1 Barnard's Loop Emission nebula -- Jonckheere 320 Planetary nebula 11.9 NGC 2194 Open cluster 8.5 Skiff Open cluster -- J0614+12.9 NGC 2175 Emission nebula -- NGC 2175.1 Open cluster -- Skiff Open cluster J0619+18.5 Object Size/Sep RA M42/M43 60' [5.sup.h] [35.0.sup.m] NGC 1973/75/77 29' x 20' [5.sup.h] [35.4.sup.m] NGC 1981 24' [5.sup.h] [35.2.sup.m] Sigma ([sigma]) 11.6", 12.9", 41.5" [5.sup.h] [38.7.sup.m] Orionis Collinder 70 4.2[degrees] x 2.0[degrees] [5.sup.h] [35.6.sup.m] Eta ([eta]) 1.8" [5.sup.h] [24.5.sup.m] Orionis Messier 78 8.4' x 7.8' [5.sup.h] [46.8.sup.m] NGC 2071 8.0' x 7.7' [5.sup.h] [47.1.sup.m] Struve 782 47" [5.sup.h] [42.9.sup.m] ([SIGMA]782) NGC 2112 11' [5.sup.h] [53.8.sup.m] Barnard's Loop 13[degrees] x 1[degrees] [5.sup.h] [54.3.sup.m] Jonckheere 320 26" x 14" [5.sup.h] [05.6.sup.m] NGC 2194 9' [6.sup.h] [13.8.sup.m] Skiff 5.0' [6.sup.h] [14.8.sup.m] J0614+12.9 NGC 2175 29' x 27' [6.sup.h] [09.7.sup.m] NGC 2175.1 5.0' [6.sup.h] [10.9.sup.m] Skiff 20' [6.sup.h] [19.4.sup.m] J0619+18.5 Object Dec. M42/M43 -5[degrees] 25' NGC 1973/75/77 -4[degrees] 47' NGC 1981 -4[degrees] 26' Sigma ([sigma]) -2[degrees] 36' Orionis Collinder 70 -1[degrees]05' Eta ([eta]) -2[degrees] 24' Orionis Messier 78 +0[degrees] 03' NGC 2071 +0[degrees] 18' Struve 782 +0[degrees] 01' ([SIGMA]782) NGC 2112 +0[degrees] 25' Barnard's Loop -6[degrees] 24' Jonckheere 320 +10[degrees] 42' NGC 2194 +12[degrees] 48' Skiff +12[degrees] 52' J0614+12.9 NGC 2175 +20[degrees] 29' NGC 2175.1 +20[degrees] 37' Skiff +18[degrees] 33' J0619+18.5 Angular sizes and separations are from recent catalogs. Visually, an object's size is often smaller than the cataloged value and varies according to the aperture and magnification of the viewing instrument. Right ascension and declination are for equinox 2000.0.
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|Title Annotation:||OBSERVING: Deep-Sky Wonders|
|Publication:||Sky & Telescope|
|Date:||Jan 10, 2018|
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