OF THE ROGER N. CLARK

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--- -- NGC 4038, NGC 4039, THE RINGT AIL GALAXY IN CORVUS NGC 4038: RA. 12h 01 .9m, Dec. -180 52 ' NGC 4039: RA. 12h 01.9m, Dec. -180 51 ' (2000.0) Technical. NGC 4038 and 4039 are interacting galaxies. The pair is known as the Ringtail Galaxy or the Antennae because of two very long, thin "tails" that extend roughly north - south from the small central part. The distance to the pair is about 50 million light-years. Recent computer models indicate the two galaxies were quite normal before their encounter, and that the tails are stars and gas flung from the outlying regions of the VISUAL ASTRONOMY OF THE DEEP SKY original galaxies. The gas, enough to form about 1.5 billion suns, has been detected at radio wavelengths, being primarily hyd. rogen. The two galaxies have probably taken several hundred million years to reach their present state. The galaxies' main portions show intricate detail. Both lack a nuclear region, and measurements of velocities show complex motions that at first seemed difficult to ex. plain. However, each galaxy is rotating about its own axis, and the two are orbiting each other. Computer models can account for the motions when this combination of orbits is considered. --:--- VISU • un 1 . ' h h al NGC 4038-39 look unusual, quite . l'ke normal galaxies. They appear as a "U" shaped object Wit t e open en d to the t The northern leg of the U appears larwes This is NGC 4038, magnitude 11.0, abge:·2.S DU by 2.5 arc-minutes in size not includthe tails. NGC 4039 is magnitude 12 and by 2.0 arc-minutes not including tails. an d 22.4 for NGC . 4039. h 8 ' h The mean surface brightness is 21.6 magnilOdes per square arc-second for NGC 4038 The parts seen m t e -mc were somehat smaller than the sizes above. Two stars" were seen, one in each galaxy. They may be two of the many bright knots that appear on photographs. If so, better skies A VISUAL ATLAS OF DEEP-SKY OBJECTS should reveal much of the intricate detail with an 8-inch. The tails are extremely faint, and it is questionable if they can be seen at all in medium size telescopes. • '. " " -- 5' -- Photograph of NGC 4038 (the bottom portion of the irregularly shaped U) and NGC 4039 (the top portion) . South is up . (Courtesy Palomar Observatory.) Drawing of NGC 4038 (the larger object) and NGe 4039 (the smaller, thin extension above it) . Scale: 1.2 arc-min/cm Viewing Distance (cm) 8-inch f! 11.5 Cassegrain 20mm Erfle ( ll 7 X) l 2,4mm Erfle (188X, best view) 25X: 115 200x: 14 50 X: 57 300x: 10 lOO X : 29 400X: 7 air mass: 1.31 , faintest star: 13.8 at zenith, 188x; no tracking 5/ l 5/83 6:45-7:04 UT at Barbers Point Hawaii' R. Clark ' , 140 141
-- --- M99 (NGC 4254), GALAXY IN COMA BERENICES RA. 12h 18.8m, Dec. 14° 25' (2000.0) Technical. M99 is a type -Sc spiral in the great Virgo Cluster of Galaxies. It is probably 50 million light-years distant and has one of the greatest red shifts in the Virgo Cluster: 2300 kilometers per second. M99 was discovered in 1781 by Pierre Mechain. It is nearly face-on and has a well-defined spiral pattern. The bright southern arm extends westward unusually far from the nucleus. This was the second galaxy to be recognized as spiral, by Lord Rosse in 1848. VISUAL ASTRONOMY OF THE DEEP SKY Visual. M99 appears at magnitude 10 4 minutes, yielding a Iw mean surface brigh_ ness of 22.2 magmtudes per square second. In the 8-inch, the arc_ central appeared as a small, bright Portion diffuse area while the spiral arms formed a soft, unifo glow around it. No hint of spiral was seen under moderate to good skies. tection of the bright southern spiral arm has been reported by observers under good excellent skies with 8-inch telescopes. with an angular size of 4.5 by 4.0 a ; : MI06 (NGC 4258), GALAXY IN CANES VENATICI R.A. 12h 19.0m, Dec. 47° 18' (2000.0) Technical. NGC 4258 was added to Messier's catalog as "M I 06" by Helen Sawyer Hogg in 1947. The galaxy appears to have erupted about 20 mi . llion years ag . . lts nucleus is unusually brIght at both VISIble and radio wavelengths. The spiral arms terminate in knots of bright young stars. "Ghost" radio arms, unseen optically, trail behind the visible arms. Two clouds of material, amounting to several tens of millions of solar masses, appear to have been ejected from the nucleus in the galaxy'S plane. Visual. M 106, magnitude 9.0, is 20 by 6.5 arc-minutes in size, though the brighter part is only 8 by 3 arc-minutes. The overall mean A VISUAL ATLAS OF DEEP-SKY OBJECTS surface brightness is 22.9 magnitudes per square arc-second. Through the 8-inch under moderate to good skies, this galaxy was quite a surprise. I was quite familiar with photographs of it and had seen it many times before, sometimes under good to excellent skies. But these observations were done at low powers before the research for this book was completed. The surprise was a distinct dark lane easily detected next to the nucleus on the west side. I t is rarely seen on photographs because the central region is usually overexposed. The lane was best seen at powers near 200x. The spiral arm to the north was also seen, though its contrast was low. The arm ended in a point about 3 arc-minutes from the nucleus. Excellent skies or larger telescopes would surely show beautiful detail in this galaxy. -- 10' -- Photograph of M99. South is up . (Courtesy Evered Kreimer, The Messier Album) Scale: 1.4 arc-min/cm 8-inch fl l1.5 Cassegrain 20mm Erfle (117 X) 12.4mm Erfle (188x, best view) 7mm Erfle (334X) Drawing of M99. Viewing Distance 25 x:98 50X:49 lOOX:25 200x :12 300x : 8 400X : 6 air mass: 1.38, faintest star: 13.8 at zenith, 1 88X; no tracking 5/ 1 5/83 10: 13-10:28 UT at Barbers Point, Hawu"iS R. Clark Photograph of MI06. South is up . (Courtesy Palomar Observatory.) Scale: 2.3 arc-min/cm 8-inch fI 1 1.5 Cassegrain Drawing of M 106. 20mm Erfle (117X) 25x:60 12.4mm Erfle (188X, best view) Viewing Distance (cm) 50X:30 300x:5 lOO X : 15 200X:7 400 x:4 air mass: 1.24, faintest star: 13.8 at zenith, 188x; no tracking 5/ 1 5/83 9: 18--9:31 UT at Barbers Point Hawaii' R. Clark ' , 142 143
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OF THE ROGER N. CLARK
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Published by Sky Publishing Corpora
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CONTENTS M78 (NGC 2068) NGC 207 1,
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PREFACE During research for this bo
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VISUAL ASTRONOMY OF THE DEEP SKY AB
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VISUAL ASTRONOMY OF THE DEEP SKY TH
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.. .. .. .. VISUAL ASTRONOMY OF THE
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e viewed with enough magnification
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lens and a piano-convex eye lens. A
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controlled depends on how many laye
Page 27 and 28: The Lumicon H-Beta Filter (Figure 3
Page 29 and 30: every 1 ° in declination and 4 min
Page 31 and 32: error of only one quarter the field
Page 33 and 34: Table 4.1. Ideal limiting magnitude
Page 35 and 36: 5 Making drawings and keeping recor
Page 37 and 38: more detail in the future. They add
Page 39 and 40: .. .. .. ... Contrast (C) C Log(C)
Page 41 and 42: VISUAL ASTRONOMY OF THE DEEP SKY A
Page 47 and 48: --- VISUAL ASTRONOMY OF THE DEEP SK
Page 49 and 50: --- M76 (NGC 650-651), PLANETARY NE
Page 53 and 54: -- -- M45, THE PLEIADES OPEN CLUSTE
Page 55 and 56: -- Brightest stars of the Pleiades
Page 57 and 58: M42 (NGC 1976), M43 (NGC 1982), THE
Page 59 and 60: --- --- --- VISUAL ASTRONOMY OF THE
Page 61 and 62: -- --- NGC 2023 NGC 2024, IC 434 (T
Page 63 and 64: --- --- M78 (NGC 2068), NGC 2071, D
Page 65 and 66: VISUAL ASTRONOMY OF THE DEEP SKY --
Page 67 and 68: --- M67 (NGC 2682), OPEN CLUSTER IN
Page 69 and 70: -- VISUAL ASTRONOMY OF THE DEEP SKY
Page 71 and 72: --- -- M82 (NGC 3034), PECULIAR GAL
Page 73 and 74: -- --- --- MI05 (NGe 3379) NGe 3384
Page 77: MI09 (NGe 3992), GALAXY IN URSA MAJ
Page 81 and 82: == -- VISUAL ASTRONOMY OF THE DEEP
Page 83 and 84: --- --- -- NGC 4449, GALAXY IN CANE
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Page 87 and 88: --- -- M90 (NGC 4569), GALAXY IN VI
Page 89 and 90: --- -- M94 (NGC 4736), GALAXY IN CA
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Page 97 and 98: -- -- VISUAL ASTRONOMY OF THE DEEP
Page 99 and 100: --- -- M83 (NGC 5236), GALAXY IN HY
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Page 111 and 112: ---------------- 5 / --------______
Page 113 and 114: --- -- VISUAL ASTRONOMY OF THE DEEP
Page 115 and 116: VISUAL ASTRONOMY OF THE DEEP SKY --
Page 119 and 120: -- -- VISUAL ASTRONOMY OF THE DEEP
Page 123 and 124: -- MI5 (NGC 7078), GLOBULAR CLUSTER
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VISUAL ASTRONOMY OF THE DEEP SKY A
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-- VISUAL ASTRONOMY OF THE DEEP SKY
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-- ·rl E I u L ro 5 +J Q) (f) 0 Y
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-- --- VISUAL ASTRONOMY OF THE DEEP
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VISUAL ASTRONOMY OF THE DEEP SKY NG
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'2 5 -rl E I U L CO '---' -t-J ill
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VISUAL ASTRONOMY OF THE DEEP SKY AP
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VISUAL ASTRONOMY OF THE DEEP SKY Ta
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-- Appendix E A catalog of deep-sky
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--- -- VISUAL ASTRONOMY OF THE DEEP
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-- -- --- VISUAL ASTRONOMY OF THE D
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--- --- VISUAL ASTRONOMY OF THE DEE
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-- -- VISUAL ASTRONOMY OF THE DEEP
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-- APPENDIX F: OPTIMUM DETECTION MA
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------- VISUAL ASTRONOMY OF THE DEE
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--- VISUAL ASTRONOMY OF THE DEEP SK
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VISUAL ASTRONOMY OF THE DEEP SKY -
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VISUAL ASTRONOMY OF THE DEEP SKY -
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G VISUAL ASTRONOMY OF THE DEEP SKY
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INDEX INDEX M70 (NGC 6681), 312, 31
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OF THE ROGER N. CLARK

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