OF THE ROGER N. CLARK

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--- VISUAL ASTRONOMY OF THE DEEP SKY A VISUAL ATLAS OF DEEP-SKY OBJECTS -- Mll (NGC 6705), OPEN CLUSTER IN SCUTUM R. A. IS h 5I.r, Dec. -06° 16' (2000.0) T chnical. M I I is a very tightly packed e n cluster that appears within the Scutum o p clo ud. In reality, however, MII is closer: sta . . h I d f ab o ut 55QO hg t-years away. ts enslty 0 t rs is as great as some of the looser globular lsters. Mll is estimated be be about 500 illion years old, however, much too young r it to be classed with the globulars. o The cluster's brightest part is about 10 arc-minutes, or about 15 light-years, across. M o st of the stars are magnitudes II to 16. Our Sun at the distance of MII would be magnitude 15.9, so the brightest stars in M I I have 100 times the Sun's luminosity. The cluster's total light is is estimated at 10 000 times that of the Sun, and its mass as nearly 3000 suns. M I I contains about 400 stars brighter than magnitude 14 and nearly 1000 brighter than 17. Visual. MII appears at magnitude 6, with a diameter of 12 arc-minutes and a mean surface brightness of about 20.0 magnitudes per square arc-second. It can be seen with the unaided eye under good to excellent skies. A 2-inch telescope will begin to show a few individual stars, and a 3-inch starts to resolve many. The cluster has a square shape, with an 8th-magnitude star near the southeast corner. In small telescopes this bright star suggests a comet nucleus and the cluster the surrounding coma. On the opposite side is a "bay" shaped like a heart. Through the 8-inch MII is spectacular at any power under skies from poor to excellent. The accompanying drawing, made under moderate skies, shows a square appearance at magnifications from 100x to 200x. The heart-shaped bay was also quite obvious. The "nebulosity" in the drawing represents unresolved background stars seen when averted vision was used - not an actual nebula. 204 205
---------------- 5 / --------______ _ -------- -- VISUAL ASTRONOMY OF THE DEEP SKY A VISUAL ATLAS OF DEEP-SKY OBJECTS --- • • • . ' ," . ,. , .... . ' . . . , . , . , . . " . -.. .. • ' . . ... , . . ... . , • .. • .. Photograph of M11. South is up. (Courtesy Ben Meyer.) cale: 0.8 arc-min/cm 'InCh f! 11. Omm Erne (11 7X) 12.5mm Orthoscopic (187X) Drawing of M 11. Viewing Distance (cm) 25x: 172 200X:21 50x: 86 300x: 14 loOx: 43 400x: 11 air mass: 1.26, faintest star: 13.6 at zenith, 187X; no tracking 9/ 1 9/82 7:05-7:20 UT at Ewa Beach Hawaii' R. Clark ' , 206 207
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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
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5 Making drawings and keeping recor
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more detail in the future. They add
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.. .. .. ... Contrast (C) C Log(C)
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VISUAL ASTRONOMY OF THE DEEP SKY A
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--- VISUAL ASTRONOMY OF THE DEEP SK
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--- M76 (NGC 650-651), PLANETARY NE
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-- -- M45, THE PLEIADES OPEN CLUSTE
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-- Brightest stars of the Pleiades
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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 and 86: -- -- --- VISUAL ASTRONOMY OF THE D
Page 87 and 88: --- -- M90 (NGC 4569), GALAXY IN VI
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 103 and 104: VISUAL ASTRONOMY OF THE DEEP SKY A
Page 107 and 108: --- VISUAL ASTRONOMY OF THE DEEP SK
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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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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
Page 137 and 138: VISUAL ASTRONOMY OF THE DEEP SKY NG
Page 139 and 140: '2 5 -rl E I U L CO '---' -t-J ill
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Page 145 and 146: VISUAL ASTRONOMY OF THE DEEP SKY Ta
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Page 149 and 150: -- Appendix E A catalog of deep-sky
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VISUAL ASTRONOMY OF THE DEEP SKY AP
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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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VISUAL ASTRONOMY OF THE DEEP SKY Ta
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VISUAL ASTRONOMY OF THE DEEP SKY Ta
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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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