In this book, Peter Manly surveys more than 150 unusual telescope designs. These are telescopes built by amateur and professional astronomers to suit some special need. There is, for instance, an inflatable telescope and one with a liquid mirror. Every so often a neglected design comes back into fashion: the largest telescopes now under construction use the alt-azimuth design that was ignored for over a century, and liquid mirror telescopes can be used for zenithal astronomy. The author shows why a particular engineering approach makes each telescope unique and explains the rationale behind the design. The effects on telescope performance are discussed where possible. This is not just a collection of weird and wonderful devices that proved to be false starts; the author also discusses the first instrument to measure star diameters and the first useful radio telescope. This book is a resource and stimulus for anyone who likes to build astronomical telescopes or is interested in the history of telescope-making.