Portable Newtonian Telescopes
By Albert Highe.
Product Information: Hardbound, 6 by 9 inches, 694 pages, 472 illustrations and 113 tables. CD not included.
Engineering, Design and Construction of Portable Newtonian Telescopes is a massive 694 page book with 472 illustrations and 113 tables that tells you how to design and build a portable Newtonian telescope that performs better, weighs less, and increases your enjoyment of its use. Simultaneously accomplishing all three of these goals requires specific knowledge and abilities many telescope builders initially do not have. Not to worry. This book helps you acquire them. The author distills his years of experience into concise descriptions of engineering principles and material properties relevant to amateur telescope making. You’ll understand how structural elements behave, and be able to evaluate and select appropriate construction materials. Reducing weight and size can make any telescope easier to move, reassemble, and store. But many steps to reduce weight also can reduce structure stiffness, increasing vibration amplitude and duration. The author explains where to look for, and how to compare, weight-reduction opportunities, and how to select and implement those with little or no impact on stiffness. The book describes the design and construction of two specific telescopes. They demonstrate that even with moderately-large instruments, you can eliminate the stepstool or ladder and be seated comfortably at the eyepiece. Their lengthy chapters, profuse with images and drawings, and extensive construction detail, will lead you through the steps required to build an attractive, functioning telescope that meets exacting goals.
In many cases, engineering equations provide sufficient insight and direction to ensure the completed telescope will meet your expectations. However, real-world structures don’t always achieve anticipated performance. The author emphasizes the importance of making decisions based on data rather than on theory or accepted lore. For example, his extensive testing of three- and four-truss structures revealed some unappreciated/unknown aspects of common practices. One of the book’s major contributions is the subsequent creation of quantitative design rules for the construction of effective telescopes. The design rules are easy to use, having been incorporated into Excel worksheets that allow even the math challenged to easily determine:
Illumination profile across telescope and eyepiece fields-of-view (influenced by of a comprehensive set of variables)
Stiffness of four-truss (eight strut) telescope structures
Stiffness of three-truss- and pseudo-truss (six strut) telescope structures
Horizontal and vertical balance of a telescope optical assembly.
Eyepiece height as a function of focuser placement and telescope elevation angle.
Deflection of straight beams with uniform cross section
Angular deflection of curved beams (simulating altitude bearings)
In-plane deflection, and out-of-plane deformation, of rings (especially applicable to minimalist upper optical assemblies)
Size and placement of bearing pads to achieve desired forces for altitude and azimuth movement
When buying a commercial telescope, or copying an existing design, one accepts the compromises made by the builder. When making your own, you can have features that no manufacturer could provide and remain profitable. The goals of anyone thinking of building a telescope should include optimized performance, weight, and comfort. There is no better introduction how to achieve them than this book.