Book review:

Star Testing Astronomical Telescopes by H R Suiter

Willmann-Bell, Inc. ISBN 943396-44-1

"I’m going to tell you a little known fact. Telescopes are easy to test. All that is required is a good high-magnification eyepiece, a conveniently placed star or illuminated pinhole, and some experience".

These are the opening words of Harold R Suiter in this unusual book. With the aid of computer-generated images of stars in and out of focus, he shows the effects of just about any kind of optical problem that can occur in a telescope, and helps you to recognize them and judge their importance. Star testing is really the ultimate way of examining optics, and will reveal even the tiniest defects of splendid instruments, and is the only tool a skillful optician like John Dobson needs to figure a mirror.

After an introduction to the basic principles comes a description of the testing procedure, and a simple review of optical errors and what they look like at the star test. You may well stop there for a good while, but when and if you are ready to go on, the tour goes on to explain in detail the star-testing procedure, and all you could possibly want to know about optical errors (and how to correct them). Misalignment, air turbulence and tube currents, pinched and deformed optics, obstruction, spherical aberration, zones, turned-down edges, chromatic aberration, astigmatism, and more - you name it, it’s there.

You will also learn about the measures of optical quality, and of fundamental concepts like the modulation transfer function, wave optics and diffraction, and many other optical tests.

This book is a true gold mine for the telescope enthusiast - in a gold mine, you may find some nuggets with little effort, but if you are willing and able, you may go on digging deeper and deeper to find more and more and more. Suiter has written an amazing book, combining the enthusiasm of the true amateur with the solid learning of a professional physicist into a comprehensive work about not only star testing, but of telescope optics in general.

This book is for you:

• If you want to learn to star test telescopes - your own or others’ - and are willing to the effort needed. "The star test’s vastness and complexity are astounding."
• If you have some experience of telescopes, and want a deeper understanding of their operation. "You will continue learning new features of the star test many years into the future".

This book is not for you:

• If you are a beginner telescope owner, or a casual observer - the subject is, contrary to Suiter’s introduction, not really easy.
• If you want to check your newly-bought Tasco telescope - you will need the experience of observing with telescopes of good as well as poor quality to evaluate its performance with any degree of confidence.
• If you want to tell what’s wrong with your friends’ telescopes - the test is sensitive enough to reveal defects in even the finest optics, and if you are not careful you may make yourself thoroughly impopular.