Some symbols don't appear here at all because they are used in different ways in different locations (a good example is N). Some that do appear here occasionally are used in alternate ways. Most of symbols are used only in the way defined in this appendix, but if readers are unsure in any case, the immediate context takes precedence.
CCD CD D DAC
nth order coefficient of aberration. speed of light propagation. acronym for charge-coupled device acronym for Compact Disc. diameter of the objective lens or mirror. acronym for digital-to-analog converter. focus shift or change in focus. 2.71828 energy.
encircled energy ratio at angular radius 8. effective focal length of the objective. the focal ratio as used in formulas. various focus positions. the '"/-number" or focal ratio. Planck's constant.
The Strehl ratio.
intensity at image point (x',yr).
Jo the zeroth-order Bessel function.
k k = 2rc/X, called the "wave number." X the wavelength of light.
MA the minor, or short axis of a Newtonian diagonal. MTF acronym for modulation transfer Mult fhe multiplier of focal lengths in the distance of the source N. v frequency (time or spatial). OTF the optical transfer function. y reduced image angle D0/1. n 3.14159 P(x,y) the pupil function at position (x,y).
R radius of curvature. rAiry radius of Airy disk.
RFT acronym for richest-field telescope. p radial coordinate of aperture (range 0 to 1). RMS acronym for root-mean-
square deviation of wavefront. 5 the sagitta in all but Appendix B. ffRMs RMS deviation of wave-
front in wavelengths. SNR acronym for signal-to-noise ratio (S/N). T distance from focal plane to center of tube. Ch. 6 and App. C. T(p) or T(x,y) transmission coefficient as a function of aperture radius. U(x',y') complex scalar field value at point (x', y').
W(p) or W(x,y) aberration over the pupil in wavelengths. x or y usually the aperture coordinates. x' ory' usually the image coordinates.
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