Astronomy: An OpenStax Textbook
This free textbook, published in 2016, is a great choice because (unlike some open-source texts), it is up-to-date and features recent scientific discoveries. It covers all topics that are traditionally taught in an introductory Astronomy course: fundamentals, solar system, stellar evolution, and galaxies. The conversational writing style is engaging, but not simplistic. Non-astronomers can enjoy reading this book while also ensuring that they are covering the hard science. See Chapters 3 and 4 for information related specifically to orbits and eclipses. The book is authored by Andrew Fraknoi, Astronomy Department Chair at Foothill College; David Morrison, senior scientist at NASA Ames Research Center; and Sidney Wolff, Emeritus Director, National Optical Astronomy Observatories.  Download the pdf version to access a rich set of indices and clickable links not found in the web version.
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University of Cambridge: Passage of Shadow of the Moon over England, 1715
Scientists have historically been highly intrigued by eclipse events. This page takes you to the 18th Century archival engraving by Edmund Halley and John Senex, depicting the passage of the Moon's shadow over England as it was observed in the total eclipse of the sun on April 22, 1715. It can be opened as a 6Mb jpeg image and viewed with remarkable clarity.
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