Astronomy appears to us as a combination of art, science, and philosophy. Its study puts the universe into perspective, giving a sense of pleasure in its beauty, awe at its immensity, and humility at our trivial place in it. From earliest human history, man has scrutinized the night sky - and wondered and marveled. With unaided eye but perceptive mind, he recognized order in the regular appearance and movements of individual objects, such as the planets and star groups (constellations), in their rhythmic and majestic progressions across the bowl of night. Even in the present era of scientific exactitude, there remains a profound awareness of mysteries beyond our present interpretations. It is only in comparatively recent years, however, that man has recognized that it takes more than conventional astronomy to account for the beauties ofthe night sky. Radiations in the Earth's upper atmosphere provide a foreground light, the study of which has come under a new name, aeronomy. The science of aeronomy has rapidly burgeoned, and the student of the light of the night sky finds that he is involved in an interdisciplinary domain.
From Day to Twilight to Night.- 1.1. The Day Sky - The Blue Planet.- 1.2. The Twilight Sky.- 1.3. The Human Eye and Its Adaptation to Low Light Levels.- 1.4. The Night Sky.- References.- Star Counts and Starlight.- 2.1. Plan of Selected Areas.- 2.2. Modified Star Counting.- 2.3. Distribution of Integrated Starlight over the Sky.- 2.4. Distribution of Starlight over the Sky.- 2.5. Photometric Map of the Sky Based on Star Counts.- 2.6. The Total Light from the Stars.- 2.7. Our Felicitous Location in the Galaxy.- Appendix 2-A. Star Gaging (Herschel) and Star Counts.- Appendix 2-B. Photometric Units in Surface Photometry.- References.- The Zodiacal Light and Gegenschein.- 3.1. Polarization of the Zodiacal Light.- 3.2. The Gegenschein.- References.- The Night Airglow or Nightglow.- 4.1. The Nightglow - Static or Dynamic?.- 4.2. Sources of Nightglow.- 4.3. Photochemical Reactions in the Upper Atmosphere.- 4.4. The Nightglow from Space: the Exosphere and Geocorona.- 4.5. Midlatitude Stable Auroral Arcs (M/SAR).- 4.6. The Polar Aurora.- 4.7. Effect of Nightglows on LONS Studies.- Appendix 4-A. The Change in Brightness of a Nightglow Layer with Zenith Distance.- References.- Dust-scattered Starlight - The Diffuse Galactic Light.- References.- Dust - Interplanetary and Interstellar.- 6.1. The Zodiacal Dust Cloud.- 6.2. Interstellar Dust.- References.- Cosmic Light and Cosmology.- References.- Epilogue.- References.