The Caldwell Objects

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172 42 nent knot of stars lies to the south of the core. The cluster is situated in a rich Milky Way field, so it is hard to discern which stars belong to the cluster and which to our galaxy's populous disk. Of course, with a really big telescope NGC 7006 reveals itself in ways that can only be imagined by the owners of small instruments. In September 1998, Brent Archinal and I observed NGC 7006 with the 31-inch reflector at the Warren Rupp Observatory in Mansfield, Ohio. The cluster was a scintillating mass of dim starlight. At high power we saw an unresolved, starlike inner core surrounded by a dark ring that defined the inner edge of a finely resolved, though jagged, outer core. With averted vision thin arms radiated out from the stellar "hole" like the limbs of a starfish wrapped around a rock. The outer halo appeared loose and fractured, as if its shell were so old and brittle that pieces of it were flaking off into space. Large-telescope users might be interested in this challenge: a tiny cluster of galaxies lies just 5' to the southwest of NGC 7006. None of these galaxies is plotted on the Millennium Star Atlas, but a few of them can be seen in the Digitized Sky Survey image on page 169.I believe they will certainly fall to large Dobsonians. Before leaving the area be sure to return to Gamma Delphini, which is a beautiful double star. The magnitude-5.2 secondary lies 9" to the west of the yellowish primary; the stars were 12" apart in 1823. Adm. William Henry Smyth saw the secondary gleam with a "light emerald" hue. The colors Smyth saw recall those of the famous double star Albireo in the nose of Cygnus, the Swan. Interestingly, though, the spectral types of Gamma Delphini's components are K1IV (primary) and F7V (secondary), respectively — basically right next to each other on the OBAFGKM sequence of stellar spectral types. So any color contrast perceived by Smyth was undoubtedly due to psychology, or intensity threshold effects in the eye. I see two golden stars, with the fainter one having a cooler (bluer) hue. But the only important question is: what do you see? Deep-Sky Companions: The Caldwell Objects
4 3 Electric Arc NGC 7814 Type: Spiral Galaxy (Sab) Con: Pegasus RA: 00 h 03.2 m Dec: +16° 09' Mag: 10.6 Dim: 5.5' x 2.3' SB: 13.4 Dist: 49 million light-years Disc: William Herschel, 1784 W. H ERSCHEL: [Observed 8 October 1784] Pretty faint, pretty large, irregularly round, easily resolvable. G C / Ν G C: Considerably bright, considerably large, (Η II-240) elongated, very gradually brighter in the middle. 4 4 NGC 7479 Type: Barred Spiral Galaxy (SBc) Con: Pegasus RA: 23 h 05.0 m Dec:+12° 19' Mag: 10.8 Dim: 3.9' x 3.0' SB: 13.4 Dist: 106 million light- years Disc: William Herschel, 1784 W . HERSCHEL: [Observed 19 October 1784] Considerably bright, much extended, gradually brighter in the middle, 4' long and 2' broad. (H I-55) The Caldwell Objects G C / Ν G C: Pretty bright, considerably large, much extended toward position angle 12°, between two stars. 43 & 44 173
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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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1003, NGC 1023, and NGC 1058 (a nic
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Way) that pop in and out of view as
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RA: 03 h 19 m 48 s Dec: +41° 30.7'
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Through the 4-inch, NGC 1275 is les
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(300,000 light-years), Pal 4 (360,0
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26 Silver Needle Galaxy NGC 4244 Ty
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2 7 Crescent Nebula NGC 6888 Type:
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Observatory, England) still lists a
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pie refractors and inefficient spec
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29 NGC 5005 Type: Mixed Spiral Gala
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s h a edges. r p However, Christian
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ulars; challenge yourself and your
Page 139 and 140: NGC 7331 is extended much farther t
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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 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: each square arcminute of its disk s
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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
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Page 217 and 218: known as NGC 2244; and NGC 2239 sho
Page 219 and 220: At a glance the two stars at the cl
Page 221 and 222: On four plates taken with the Bruce
Page 223 and 224: years. A total of 43 star-cluster c
Page 225 and 226: 5 2 NGC 4697 Type: Elliptical Galax
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Page 229 and 230: 53 The Spindle NGC 3115 Type: Lenti
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Page 233 and 234: 5 4 NGC 2506 Type: Open Cluster Con
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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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5 8 NGC 2360 Type: Open Cluster Con
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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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9 5 NGC 6025 Type: Open Cluster Con
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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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