This book provides a unified treatment of the characteristics of telescopes of all types, including telescopes
whose performance is set by geometrical aberrations and the effect of the atmosphere, and those diffraction-limited
telescopes designed for observations from above the atmosphere. The emphasis throughout is on basic principles,
such as Fermat's principle, and their application to optical systems specifically designed to image distant celestial
sources. Astronomical Optics, Second Edition also contains thorough discussions of the principles underlying all
spectroscopic instrumentation, giving special emphasis to grating instruments used with telescopes. An introduction
to adaptive optics provides the needed background for further inquiry into this rapidly developing area.