Features such as guiding and adaptive optics are now common even on small telescopes. In fact, for bright targets, small ground-based scopes can sometimes give higher resolution than large ones. Therefore, both of these books are useful for amateur astronomers as well as professionals.

The Design and Construction of Large Optical Telescopes
by Pierre Y. Bely, Ed.

Reviewed by

Outstanding introduction to the instrumentation used in modern optical (visible and infrared) astronomy. Although the basic equations are given, the treatment is not primarily mathematical. Discusses large and small telescopes, detectors, mirrors, guiding, pointing and control, observatories and siting, adaptive optics, and mechanical engineering considerations of large telescopes and enclosures. For big projects, project management is important: the cost of a telescope, the authors say, grows as the 2.6th power of the diameter of the primary mirror, while its mass, and the cost of the enclosure, increase almost as D^3. In the future, real estate costs and the cost of complying with ever-increasing government regulations will probably comprise the biggest expense.

The section on optics provides an excellent semi-technical introduction to point-spread functions, the classical optical aberration equations, and the fabrication of large mirrors. Most large telescopes today use a Ritchey-Chrétien design on Alt-az mounts. The main disadvantage of this configuration, besides their inability to look straight up, is the need for field derotators. In fact, when viewing a wide field (over one arcminute), field derotators are impractically large and the only effective solution is to rotate the observer. This might explain the lack of enthusiasm by astronomers for direct visual observations these days.

Even though it's mostly about large telescopes (including large space telescopes like the HST), the information is just as relevant, and perhaps even more essential, to users of small ones. For example, page 287 has a table of the number of guide stars of a given magnitude in the V, J, and K-bands per square degree. Gear drives, say the authors, are no longer used for pointing, having been replaced by direct drive linear motors. In space, using motors doesn't work, and space telescopes use heavy rotating wheels which absorb and release angular momentum as needed. There are also formulas for calculating the effects of wind and for modeling structural vibrations, which are important for scopes of all sizes.

Jan 01, 2012

The Principles of Astronomical Telescope Design
by Jingquan Cheng

Reviewed by

This is a more detailed and technical discussion of telescope design. This book is distinguished by the huge breadth of subject matter: telescopes for optical, radio, millimeter wave, infrared, and X-ray radiation, and even telescopes and detectors for gravitational waves, dark matter, and neutrinos are discussed in detail. Equations for mirror design, mountings, and stuctural analysis are derived and clearly explained. The reader is expected to have a basic understanding of calculus, optics and of the different types of telescopes. It also mentions future technologies, such as interferometric imaging and photon sieves, which promise to revolutionize optical astronomy. The illustrations are mostly line drawings, and are of poor quality, which is surprising for a Springer book. However, most are readable. Translated from Chinese. This book might not be a page-turner, but the writing is remarkable in its clarity.

Jan 02, 2012