# Astronomical Optics (2nd Edition)

## Daniel J. Schroeder

Language: English

Pages: 495

ISBN: B000LSBPD2

Format: PDF / Kindle (mobi) / ePub

This book provides a unified treatment of the characteristics of telescopes of all types, both those 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.

The book also contains thorough discussions of the principles underlying all spectroscopic instrumentation, with special emphasis on grating instruments used with telescopes. An introduction to adaptive optics provides the needed background for further inquiry into this rapidly developing area.

* Geometrical aberration theory based on Fermat's principle

* Diffraction theory and transfer function approach to near-perfect telescopes

* Thorough discussion of 2-mirror telescopes, including misalignments

* Basic principles of spectrometry; grating and echelle instruments

* Schmidt and other catadioptric telescopes

* Principles of adaptive optics

* Over 220 figures and nearly 90 summary tables

Stargazing Basics - Getting Started in Recreational Astronomy

Observing and Measuring Visual Double Stars

Fig. 5.3 is shown in Fig. 5.7. Note that this map shows a wavefront that is both 5.3. Ray and Wavefront Aberrations 81 Fig. 5.6. Wavefront aberration map for image with spherical aberration. The image is located at the paraxial focus. See Figs. 4.5 and 4.6 for ray and spot diagrams. advanced and retarded. The portion that is advanced is higher than the center, while the retarded part is lower. A useful exercise for the reader is to correlate the ray directions in Fig. 5.2 with the shape of.

Summary, then, the paraboloid telescope is limited to small fields with coma setting the field limit. All other aberrations are negligible over this field. 6.2. TWO-MIRROR TELESCOPES We introduced the topic of two-mirror telescopes in Chapter 2 with schematic diagrams of two types, Cassegrain and Gregorian, in Fig. 2.7, as well as a set of definitions of normalized parameters with which to describe any two-mirror telescope. Selected items from Section 2.5 and Table 2.1 are summarized in Table.

&. 0.20 «*. ,.•••*' A »^ ^ i * 0.10 0.00 -0.10 .•"1 "•^^Nv •Tr- O s ^ ••.^^^^ - -0.20 -10 ••*•*'*** •••**' ^ .^^ "^"--» • 1 -5 I 1 1 ^ 1 \ 1 • 0 5 Field ongle (orc-min) 10 Fig. 6.7. Angular astigmatism (solid line) for Ritchey-Chretien telescope misaligned along ;;-axis. The AA is the sum of astigmatism for aligned telescope (dotted line) and linear astigmatism (long dashed line). Parameters of the telescope are given in Table 6.10; tilt and decenter parameters are.

The principal effect a decentered and tilted astigmatic focal surface. It is also evident from Fig. 6.7 that the effect of linear astigmatism leads to differences 142 6. Reflecting Telescopes g s tf*^lli^j(> -260 SURFACE: IMfl 130 130 260 THROUGH FOCUS SPOT DinGRflM RITCHEY-CHRETIEN MISRLIGNED WED FEB FIBJ) RHS RflOIUS GEO RROIUS SCALE BflR 3 : : : 1999 1 0.103 0.156 56.2 2 1.513 2.050 3 H.0S8 5.500 REFERENCE SPOT S I Z E U N I T S ARE MICRONS, CHIEF RflY Fig. 6.9. Through-focus.

^^il^iAssuming the plate of index n is in air, n^ = «2 = 1, n\ = n2 = n, and noting that ^2 = "^i — ^? we get s\ = ns^, S2 = Si — (d/n). The distance from object to image is A = 5*2 — ^2 + ^» or A = 41 -(l/n)]. (2.4.5) Note that the displacement A is independent of the object distance and, as is true in all cases in the paraxial approximation, independent of height y. For a typical glass with n= 1.5, we see that A = d/3. In the paraxial approximation an optical system is free of any.