Out of the Blue: A 24-Hour Skywatcher's Guide

by John Naylor

• ISBN13: 9780521809252
• ISBN10: 0521809258
• Format: Hardcover
• Copyright: 2002-11-18
• Publisher: Cambridge University Press

Summary

Why is the sky blue and why are sunsets red? When can I see a rainbow? Why is the moon sometimes visible in daylight? In Out of the Blue skywatcher John Naylor offers practical advice about where and when you can expect to see natural phenomena, what you will see and how to improve your chances of seeing it. Naylor takes in both the night and the day sky, and deals only with what can be seen with the naked eye. Drawing on science, history, literature and mythology, and assuming only basic scientific knowledge, Out of the Blue is for everyone who enjoys being outdoors and who feel curious or puzzled about things optical and astronomical. John Naylor was born in England, but spent his childhood in Peru. A graduate of London University with a degree in philosophy, he teaches physics at a secondary school in London.

Table of Contents

Preface	xi
Introduction	1	(4)
Daylight	5	(24)
The colour of the daytime sky	5	(2)
Why is the sky blue?	7	(4)
Airlight	11	(3)
Aerial perspective	14	(4)
How far can you see?	18	(2)
Polarised light	20	(1)
Polarised light from the sky	21	(4)
Polarised light due to reflections	25	(2)
Haidinger's brush	27	(2)
Shadows	29	(21)
No light without shadow	29	(1)
Solar shadows	30	(3)
Shadows formed by point sources	33	(2)
Mach bands	35	(1)
Coloured shadows	36	(3)
The heiligenschein	39	(4)
Shadows on water	43	(3)
Shadows formed by clouds	46	(2)
Shadows under trees in leaf	48	(2)
Mirages	50	(14)
Atmospheric refraction	50	(3)
Inferior mirages	53	(4)
Superior mirages	57	(4)
Lake monsters	61	(1)
Looming and unusual visual range	62	(2)
Sunset and sunrise	64	(24)
Sunset	64	(6)
Twilight	70	(3)
Clouds at sunset	73	(2)
The purple light	75	(2)
Crepuscular rays	77	(2)
Mountain shadows	79	(1)
Abnormal twilights	79	(1)
The Sun at the horizon	80	(4)
Green flashes	84	(2)
The Purkinje effect	86	(2)
Rainbows	88	(39)
Unweaving the rainbow	88	(3)
How to recognise a rainbow	91	(4)
Looking for rainbows	95	(2)
Supernumerary bows	97	(2)
Circular rainbows	99	(2)
Rainbows at sunset and sunrise	101	(1)
Lunar rainbows	102	(1)
Reflection rainbows	103	(2)
Reflected rainbows	105	(1)
Spray bows	106	(1)
Fog bows	106	(2)
Rainbow wheels	108	(1)
Horizontal rainbows	109	(2)
Searchlight rainbows	111	(1)
Eclipse rainbows	112	(1)
Anomalous rainbows	112	(2)
Explaining the rainbow	114	(8)
Tertiary rainbows	122	(1)
Polarised rainbows	123	(1)
Are rainbows real?	123	(2)
Notes for rainbow observers	125	(2)
Coronae and glories	127	(9)
Coronae	127	(3)
Other situations in which coronae are seen	130	(1)
Cloud iridescence	131	(2)
Glories	133	(2)
Notes for observers of coronae and glories	135	(1)
Atmospheric halos	136	(21)
Ice halos	136	(3)
22° halo	139	(5)
Upper tangent arc	144	(1)
46° halo	144	(1)
Rare halos	145	(1)
Parhelia	146	(3)
Circumzenithal and circumhorizontal arcs	149	(2)
The parhelic circle	151	(1)
Sun pillars	152	(1)
Subsuns	152	(2)
Notes for ice halo observers	154	(3)
The night sky	157	(14)
A brief history of the sky	157	(4)
Naked-eye astronomy	161	(2)
The celestial sphere	163	(2)
The ecliptic	165	(2)
The apparent motion of the Sun	167	(2)
Why is the sky dark at night?	169	(1)
The sky beyond the equator	170	(1)
The Moon	171	(48)
Observing the Moon	171	(1)
The Earth-Moon system	172	(4)
Looking at the Moon without a telescope	176	(4)
The lunar surface	180	(3)
The best time to look at the Moon	183	(2)
The Moon in daylight	185	(3)
How bright is the Moon?	188	(5)
Earthshine	193	(2)
Moonlight	195	(2)
The Moon illusion	197	(1)
A Blue Moon	198	(1)
Sidereal and synodic months	199	(1)
Finding the Moon in the sky	200	(4)
Moonrise and moonset	204	(3)
The lunar day	207	(1)
Libration	208	(2)
Lunar puzzles	210	(3)
The Moon's phases	213	(6)
Eclipses	219	(21)
Chasing eclipses	219	(1)
Solar eclipses	220	(2)
Preparing to see an eclipse	222	(2)
Watching a solar eclipse	224	(3)
Eclipse checklist	227	(4)
Explaining a solar eclipse	231	(5)
Eclipses of the Moon	236	(4)
Planets	240	(18)
The Solar System	240	(6)
How to tell a planet from a star	246	(3)
Inferior and superior planets	249	(1)
Where to look for an inferior planet	250	(2)
Mercury	252	(1)
Venus	252	(2)
Where to look for a superior planet	254	(2)
Apparent changes in brightness of superior planets	256	(2)
Stars	258	(24)
Light without form	258	(3)
Where are the stars?	261	(5)
Star brightness	266	(5)
Star colours	271	(1)
Looking at stars through a telescope	272	(2)
Why do stars twinkle?	274	(1)
Seeing in the dark	275	(2)
Peripheral vision	277	(1)
Why are stars star-shaped?	277	(1)
Constellations	278	(4)
Comets and meteors	282	(18)
Comets	282	(5)
Meteors	287	(6)
Artificial satellites	293	(1)
Aurorae	294	(3)
Zodiacal light	297	(3)
APPENDIX: Technical and practical advice for skygazing	300	(6)
Estimating distance	300	(1)
A primer on angles	301	(1)
Binoculars	302	(2)
A cloud primer	304	(2)
Glossary	306	(10)
Further reading	316	(3)
Sources and notes	319	(26)
Index	345