OF THE ROGER N. CLARK

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-- -- --- --- NGC 4565, EDGE-ON GALAXY IN COMA BERENICES R. A. 12 h 36.4m, Dec. 25° 59' (2000.0) Technical. NGC 4565 is a marvelous galaxy that is oriented only 4° from perfectly edgeon. It is probably an outlying member of the Virgo Cluster. Its distance is thought to be about 20 million light-years, and its apparent length at that distance corresponds to about 90 000 light-years. Its total light is estimated to be about 3 billion times that of our Sun. The entire length of the galaxy exhibits dark dust lanes. High-resolution photographs show beautiful, intricate detail in the dust lanes reminiscent of the festoons seen on Jupiter. The gravitational and magnetic fields in a spiral galaxy tug at the dust clouds, density waves compress them, and clouds' collide with one another. This continual energy input causes upwellings that often reach hundreds of light-years above the galactic plane. As clouds fall back to the plane of the rotating galaxy, their paths form arcs that produce the festoon features. This is a common occurrence in spiral galaxies, but here we can view it especially clearly. The features in NGC 4565 are quite small in angular size, appearing no more than 5 arc-seconds wide and 10 to 15 arc-seconds long. VISUAL ASTRONOMY OF THE DEEP SKY Visual. NGC 4565 is a spectacular sight i medium and large amateur telescopes. Thi alaxy is . fte verlooked by amate urs, but m my opmlOn It IS one of the most beautifu l in the sky, being more spectacular than M I04 the commonly observed, nearly edge-o galaxy 37° to the s uth. !he visual magni_ tude of NGC 4565 IS 10.5, ItS apparent size is 15 by 1.1 arc-minutes, and its mean surface brightness is 22.2 magnitudes per square arcsecond. Through the 8-inch in moderate to good skies, the dark lane was quite easily seen without averted vision by several observers at powers from 117 to 188x. I had viewed this galaxy several times in poorer skies at lower powers without Spotting the dark lane. At 188x in a 12.4-mm Erfle eyepiece, the galaxy stretched about halfway across the 23 arc-minute field of view. The nuclear region showed detail rarely seen in photographs, because they usually overexpose the center in order to show the faint outer parts; the nucleus itself appeared like a bright star. The intensity dropped fairly rapidly for the first 10 arc-seconds or so, then about 25 arc-seconds on each side of the nucleus, in the plane of the galaxy, two bright spots were seen that also rarely appear in photographs. Apparently, dust clouds darken the region between the nucleus and the spots. When this observation was made, none of the observers had seen photographs of the nuclear region, so the details were a pleasant discovery. More details are in the description on page 55 (Chapter 5). A VISUAL ATLAS OF DEEP-SKY OBJECTS Photograph of NGC 4565. South is up. (Courtesy Palomar Observatory.) ---5' -- Drawing of NGC 4565. Scale: 1.2 arc-min/cm 8-inch fi lLS Cassegrain 20mm Erfle (117 X) 12.4mm Erfle (188X, best view) Viewing Distance (cm) 25X:115 200X:14 50 X: 57 300x: 10 100x: 29 400x: 7 156 air mass: 1.21, faintest star: 14.3 at zenith, 188x; no tracking 5/1 1/83 10:00--10:42 UT at Waianae ranch Hawaii; R. Clark 157 '
--- -- M90 (NGC 4569), GALAXY IN VIRGO R.A. 12h 36.8m, Dec. 13° 09' (2 000.0) Technical. M90 is a spiral galaxy in the Virgo Cluster. Its distance is about 40 million light-years and its diameter about 80 000 light-years. The galaxy has been estimated to weigh about 80 billion solar masses. It was discovered by Charles Messier in 1781. VISUAL ASTRONOMY OF THE DEEP SKY - Visual. M90 appears at magnitude 9.0, with an apparent diameter of 7 by 2.5 arc-minutes The mean surface brightness is 20. 7 magni tudes per square arc-second. The nUcleus appears like an 11 th-magnitude star, surrounded by the galaxy's faint oval glow. No details were seen in the 8-inch under mo der_ ate skies, though numerous dark dust lanes appear near the bright central region on photographs. A large amateur telescope or better skies may begin to show these. Only the innermost 4.5 by 0.9 arc-minutes of the galaxy was seen; the outer spiral arms are very fa int. A VISUAL ATLAS OF DEEP-SKY OBJECTS \ • ---5' --- Photograph of M90. (Courtesy Evered Kreimer, The Messier Album.) Scale: 1.2 arc-min/cm 8-inch f/ 1 1.5 Cassegrain 20mm Erfle (117X) 12.4mm Erfle (188 X, best view) Drawing of M90. Viewing Distance (cm) 25X:1l5 200X:14 50 x: 57 300X: 10 100x: 29 400X : 7 air mass: 1.38, faintest star: 13.8 at zenith, 188 x; no tracking 5/15/83 10:31-10:41 UT at Barbers Point Hawaii' R. Clark ' , 158 159
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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
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The Lumicon H-Beta Filter (Figure 3
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every 1 ° in declination and 4 min
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error of only one quarter the field
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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
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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 and 78: MI09 (NGe 3992), GALAXY IN URSA MAJ
Page 79 and 80: -- --- M99 (NGC 4254), GALAXY IN CO
Page 81 and 82: == -- VISUAL ASTRONOMY OF THE DEEP
Page 83 and 84: --- --- -- NGC 4449, GALAXY IN CANE
Page 85: -- -- --- VISUAL ASTRONOMY OF THE D
Page 89 and 90: --- -- M94 (NGC 4736), GALAXY IN CA
Page 93 and 94: -- VISUAL ASTRON0MY OF THE DEEP SKY
Page 95 and 96: -- --- -- VISUAL ASTRONOMY OF THE D
Page 97 and 98: -- -- VISUAL ASTRONOMY OF THE DEEP
Page 99 and 100: --- -- M83 (NGC 5236), GALAXY IN HY
Page 109 and 110: --- -- VISUAL ASTRONOMY OF THE DEEP
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
Page 133 and 134: -- ·rl E I u L ro 5 +J Q) (f) 0 Y
Page 135 and 136: -- --- 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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