Astronomy is a popular subject for non-science majors in the United States, often representing a last formal exposure to science. Online learning environments are increasingly important in the landscapes of higher education and lifelong learning. The number of students taking online classes is growing, and more instructors are being asked to take their teaching online. This practical guide is intended for astronomy instructors who want to develop their first online course as well as those who want to add new tools and experiences to their existing courses. It explores online course design, integrating new and social media into online learning experiences, adaptive learning systems, massive open online classes (MOOCs), and the use of virtual worlds and virtual reality to teach astronomy. Key Features Encapsulates current practices in online astronomy education Focuses on learning using real data and accurate simulations Provides practical advice on creating a massive open online class Tailored to the differing needs of formal and informal leaners Includes state-of-the-art adaptive learning technologies At a time when the coronavirus is still having a severe effect on schools and universities, on-line learning is very much in evidence, and this book is a very up-to-date and comprehensive guide to how it is best approached, particularly for astronomy. The Observatory, Vol. 141 2021 June