The Caldwell Objects

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37 But until we have the ability to go back in time ... to peer over [Herschers] shoulder as he was sweeping, I don't think we'll ever know for sure exactly what NGC 6882 is." To find NGC 6885 first use your naked eye and look about 10° (one fist's width) southwest of Epsilon (ε) Cygni, the elbow of the celestial Swan's southern wing, or a similar distance (actually 9°) east-southeast of Beta (β) Cygni (Albireo), the famous telescopic double star marking the Swan's nose. There you will find the 6th-magnitude star 20 Vulpeculae huddled with two other similarly bright stars (18 Vulpeculae and 19 Vulpeculae) in a ½°-wide patch of sky; 20 Vulpeculae is the southernmost of the three. Two Tin-magnitude stars also accompany 19 Vulpeculae, and the entire naked-eye region looks like a speckled haze about the size of the full Moon. This haze is not caused by NGC 6885, which shines below the limit of naked-eye visibility at magnitude 8.1, but by an optical effect that spins closely knit stars into webs of imaginary wispiness. (Messier masters may prefer to star-hop to 20 Vulpeculae from M27, the Dumbbell Nebula, about 5° to the southwest.) I should mention that some references include 20 Vulpeculae in the cluster's total brightness. The second edition of Sky Catalogue 2000.0, for instance, lists the cluster's photographic magnitude as 5.7. But this gives observers unrealistic expectations. Even under a dark sky one could easily miss NGC 6885 with a sweep of 7x35 binoculars because 20 Vulpeculae overwhelms its dim light, which looks like a burp of "gas" just southwest of that star. The cluster might well be lost entirely under city lights. With the nearly 3° field of the Genesis at 23x, the region including 18, 19, and 20 Vulpeculae looks like a cluster being ripped apart by some unseen tidal stress; the densest popu- 148 lation of stars near 20 Vulpeculae is a crumbling "comet" with a wide parabolic hood of starlight and a tail that flows northward toward 19 Vulpeculae. Look for a bar of fuzzy starlight 6' northwest of 20 Vulpeculae, oriented eastnortheast to west-southwest; this is the concentration of stars in NGC 6885 that Trumpler classified as NGC 6882. An obvious trapezoid of stars appears immediately to the southwest of 20 Vulpeculae. At 72x a conspicuous pair of stars lies immediately to the northeast of 20 Vulpeculae, while a dozen or so fainter suns lie to the east. A rough line of equally spaced 11th- to 12thmagnitude stars slice through the fuzzy bar of light, which contains still fainter suns popping in and out near the limit of visibility. Doubling the magnification spreads out the stars farther, providing the best view of William Herschel's "cluster of coarsely scattered stars." In total some 35 stars populate the 20'-wide cluster when counted down to 12th magnitude; 60 members can be tallied down to 13th magnitude. Other suns make up the Milky Way backdrop. A nice l0th-magnitude topaz star lies just to the northeast of 19 Vulpeculae, itself a red-tinted type K3I-II giant. Now return to low power. In a 2° field of view crisscrossing corridors of darkness can be seen in the region directly south of NGC 6885. The view is best if 18 Vulpeculae is placed at the northern end of the field of view. One corridor begins at 19 Vulpeculae and ends just east of the roughly 5th-magnitude variable (and tight double) star QR Vulpeculae, about 1.5° to the southeast. Another begins on the western end of NGC 6885 and ends to the west of QR Vulpeculae. A third corridor lies farther to the west and is paralleled by a sharp needle of dark nebulosity, also to the west. Two perpendicular dark alleys can also be seen in the southern end of this field. The challenge is to Deep-Sky Companions: The Caldwell Objects
see the dark needle near the third corridor in 7x35 binoculars. I thought I'd wrap up this discussion by going back to the beginning and leaving you with one final forehead-slapping bit of information. Despite everything that you've read, Archinal reminds us that it's still entirely possible that the clustering of stars to the northwest of 20 Vulpeculae is a separate physical group. A1961 McDonald Observatory study of 15 stars in the area concluded that NGC 6885 37 might be "an association around NGC 6882," with both being at a distance of 1,950 light-years. And yet "the status of NGC 6885 is quite uncertain," says French cluster expert Noel Robichon, and Douglas Geisler (University of Concepcion, Chile) sees "no strong indication" that either NGC object is really a star cluster. "So keep in mind," Archinal cautions, "that we just don't know" exactly how many clusters populate this unassuming but controversial corner of the northern Milky Way. The Caldwell Objects 149
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DEEP-SKY COMPANIONS The Caldwell Ob
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DEEP-SKY COMPANIONS The Caldwell Ob
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Contents Foreword by Patrick Moore
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to be more difficult than others, s
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years of thought and observation ar
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XII position, type, angular size, a
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sky and share its splendors. There
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CHAPTER 1 About This Book O N ONE S
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times vog can back up and cause a s
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when there is moisture in the air.
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Herschel's original observations, p
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we use today and to one another? I
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SIMBAD (Set of identifications, Mea
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Caldwell 26. The objects in the Cal
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tion near the edges of the charts).
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nights of observing. Unless otherwi
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CHAPTER 2 The Caldwell Objects 1 1
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Because of its location far from th
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as strongly energized as would be e
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suggested by the patchiness of NGC
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4 NGC 7023 Type: Reflection Nebula
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astronomers found direct evidence o
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and his contemporaries. Why then wa
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6 Cat's Eye Nebula NGC 6543 Type: P
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Eighth-magnitude NGC 6543 is locate
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7 NGC 2403 Type: Mixed Spiral Galax
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according to theory, the gas densit
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8 Ghost’s Goblet NGC 559 Type: Op
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One other thing adds to the cluster
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RA: 22 h 56.8 m Dec: +62° 37' Mag:
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nebula is a near impossibility, eve
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1 0 The Horseshoe Cluster NGC 663 T
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heart of the cluster, dividing it i
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appears to be the edge of a rapidly
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1 2 NGC 6946 Type: Mixed Spiral Gal
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to the west by a row of similarly b
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the south-southwest. NGC 457, howev
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photographs. The cluster's bright "
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play begins at 8:00 p.m., when my e
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ightness by summing the contributio
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jewels. Here are sapphires, rubies,
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15 outer shell falls upon the retin
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"knots" have also been noted by exp
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tight gathering of a half-dozen rou
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1 7 NGC 147 Type: Elliptical Galaxy
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the center. A faint outer halo is a
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1 9 Cocoon Nebula IC 5146 (nebula)
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trickle into the pool surrounding t
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2 0 North America Nebula NGC 7000 T
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egion's size and mass extreme when
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The Caldwell Objects 20 87
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2 1 Box Galaxy NGC 4449 Type: Irreg
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fuse but obvious glow of patchy lig
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qualifier—the word "light" — ha
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with a sheen of light, especially a
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Page 119 and 120: RA: 03 h 19 m 48 s Dec: +41° 30.7'
Page 121 and 122: Through the 4-inch, NGC 1275 is les
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Page 125 and 126: 26 Silver Needle Galaxy NGC 4244 Ty
Page 127 and 128: 2 7 Crescent Nebula NGC 6888 Type:
Page 129 and 130: Observatory, England) still lists a
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Page 133 and 134: 29 NGC 5005 Type: Mixed Spiral Gala
Page 135 and 136: s h a edges. r p However, Christian
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Page 139 and 140: NGC 7331 is extended much farther t
Page 141 and 142: away" stars escaped the confines of
Page 143 and 144: sweep the telescope in a north-sout
Page 145 and 146: highly suspect by some. However, in
Page 147 and 148: 33 Network Nebula; Bridal Veil Nebu
Page 149 and 150: A quarter-second later, the star en
Page 151 and 152: under the dark skies of Seagrave Ob
Page 153 and 154: 35 NGC 4889 Type: Elliptical Galaxy
Page 155 and 156: magnitude 12.2 some 18' to the east
Page 157 and 158: 36 NGC 4559 Type: Mixed Spiral Gala
Page 159 and 160: Comae Berenices, the obvious northe
Page 161 and 162: 3 7 NGC 6885 Type: Open Cluster Con
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Page 165: of Herschel's telescope. W then e e
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Page 173 and 174: not be found in planetary nebulae,
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Page 177 and 178: 4 0 NGC 3626 Type: Lenticular Galax
Page 179 and 180: 40 NGC 4546 in Virgo, NGC 4138 in C
Page 181 and 182: Northern Hemisphere, and people cel
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Page 185 and 186: this state of affairs.) The Hyades
Page 187 and 188: 4 2 NGC 7006 Type: Globular Cluster
Page 189 and 190: each square arcminute of its disk s
Page 191 and 192: 4 3 Electric Arc NGC 7814 Type: Spi
Page 193 and 194: hook as my "train route." Start at
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Page 197 and 198: 4 5 NGC 5248 Type: Mixed Spiral Gal
Page 199 and 200: of the field. Those living under da
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Page 205 and 206: 4 7 NGC 6934 Type: Globular Cluster
Page 207 and 208: stragglers are stars that appear to
Page 209 and 210: 4 8 NGC 2775 Type: Spiral Galaxy (S
Page 211 and 212: with a CCD camera — discovered a
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known as NGC 2244; and NGC 2239 sho
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At a glance the two stars at the cl
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On four plates taken with the Bruce
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years. A total of 43 star-cluster c
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5 2 NGC 4697 Type: Elliptical Galax
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northeast of the sixth star in the
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53 The Spindle NGC 3115 Type: Lenti
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and the 100-inch telescopes atop Mo
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5 4 NGC 2506 Type: Open Cluster Con
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emerge, followed by a diffuse outer
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perfection than is actually the cas
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jets, like a stream of water from t
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5 6 Pac-Man Nebula NGC246 Type: Pla
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the triple-alpha process, wherein t
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5 7 Barnard's Galaxy NGC 6822 Type:
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to show how the galaxy's western re
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core and limber arms, which, he wro
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esembles Jupiter . . . '" Smyth's f
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years" and suggests amateurs monito
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6 0 Ringtail Galaxy; Rataail Galaxy
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war. X-ray images taken by the Rosa
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W. Sinnott's NGC 2000.0 has a visua
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62 Milkweed Seed Galaxy NGC247 Type
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through the narrow haze. But give t
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was more readily seen in binoculars
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Society. Accepting that distance, w
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any large telescope that can provid
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ought it to our attention in the Fe
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inch the cluster shows a pyramid of
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NGC 253 is the brightest member of
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magnitude stars, one just to the ea
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6 6 NGC5694 Type: Globular Cluster
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you see its core dancing? Its starl
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cosmologist Halton Arp (Max-Planck
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and kinked. All this detail is wrap
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telescope. But seeing it takes more
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streamers begin to appear, but they
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tounding, because NGC 6302 is a mag
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70 Southern Pinwheel NGC300 Type: S
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would John Herschel suddenly fault
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Dunlop discovered NGC 55 with his 9
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even when crossing the meridian. Co
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"nebulous clusters" (Class II); and
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galaxy's disk and halo. NGC 2477 ap
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condensed, almost to the very margi
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The asymmetry remains at high power
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other popular nickname, the Eight-B
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longed look, the object displays a
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times larger than the full Moon. In
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emains of a globular cluster that w
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he classified them accordingly. NGC
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NGC 6231). Under averted vision the
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7 7 Centaurus A NGC5128 Type: Pecul
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Harvard College Observatory's 24-in
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at 16 million light-years. If you s
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78 NGC 6541 Type: Globular Cluster
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seems to fragment into tiny stars,
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sense, evinced by any known cluster
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12th-magnitude double star. The clu
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original with Bayer, but goes back
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Omega Centauri is generally regarde
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glitter all come to mind as the clu
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shattered remains of their diminuti
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It's a nice even disk of l0th-magni
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with the fiery reddish light of hyd
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nebulosity when he viewed the regio
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the two jets of radio-wave-emitting
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pair of tweezers. A fairly bright s
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suggest that our universe may be on
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8 5 Omicron Velorum Cluster IC2391
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Nicolas Louis de Lacaille, however,
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much sky as does the full Moon, tho
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8 7 NGC 1261 Type: Globular Cluster
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timates, making it 2 billion years
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NGC 5822. Don't be surprised if you
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89 S Normae Cluster NGC 6087 Type:
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fact, if you look about 7' southwes
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lowing night fell clear, when Hersc
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NGC 2867 is a nitrogen-rich planeta
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halfway between M37 in Auriga (200
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9 2 Eta Carinae Nebula GC 3372 Type
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anch of cold, dark material. Indeed
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stretch 16 billion km from the cent
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the object was known to some civili
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east, and a dim lip of gas to the s
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1 0 1 NGC 6744 Type: Barred Spiral
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have been identified in NGC 6752's
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ightest spiral arm(s) to the north,
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his maiden voyage of discovery in 1
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simply takes much too much effort t
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very wide double of near-equal inte
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went out and looked at the cluster
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NGC 2516 is 60 million years young
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and contains some 1,890 members, wh
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9 8 Coalsack Cluster NGC 4609 Type:
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it near the Swan? There is a still
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with the naked eye is a challenge.
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1 0 0 Lambda Centauri Cluster Colli
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position updates to (2000.0) R.A. 1
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Eta Carinae Nebula. But remember th
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9th magnitude. Of the latter, 23 ha
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103 1 0 3 Tarantula Nebula; True Lo
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southern-sky explorer Abbe Nicolas
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ters it has had thus far with the g
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ly east of NGC 362 we find the magn
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the eye ever inward and takes your
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1 0 5 Southern Butterfly NGC 4833 T
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stars"). Lacaille also likened NGC
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is about 7' in length, and nearly 2
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evealed a significant blue-straggle
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ightest stars shine around 4th magn
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egion looks cold and disturbing, no
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The galaxy received some incidental
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This entry is obviously in error, b
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7 N G C 4 0 4 T y L p e n : G t a i
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pointed her 7x35 binoculars toward
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13 NGC 288 Type: Globular Cluster C
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your telescope on Eta Sculptoris an
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19 N G C 6 2 8 1 T y O p e C : n l
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C Name Type Con. R.A. Dec Mag. Size
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C Name Type Con. R.A. Dec Mag. Size
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Appendix B Why Messier Did N o t i
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A typical pattern for evening hunti
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Earth turns, the cluster would clim
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Initially Herschel made his living
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of the heavens with it. For his swe
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tube's front end. This meant that t
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Star in Collo Ceti" about the star
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years, Herschel would observe some
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fluid, but added that ages of obser
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Appendix D Photo Credits in order o
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A Abell426, 101 Acrux, 388, 392, 39
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index Caldwell 44, 173, 176-178 Cal
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and nebulae, 271, 274, 362 and open
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Hevelius, Johannes, 72, 81, 452 Hip
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M103, 49-50, 58-59 M110, 77 MACHOs.
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NGC 3324, 369 NGC 3372 (Caldwell 92
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Perseus Cluster, 101 Phi Cas Cluste
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Τ Tarantula Nebula (Caldwell 103),
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