Spectrograph Design Fundamentals

Preface     ix
Acknowledgements     xi
A brief history of spectroscopy     1
The relevant regions of the electromagnetic spectrum     6
The limits of optical spectrography     8
Geometrical optics     10
Rays and wavefronts     10
Instrumental optics     11
Centred systems     12
Gaussian optics     12
Optical layout     20
Apertures, stops, fields, irises and pupils     20
Ray bundles     23
The Helmholtz-Lagrange invariants     23
Surface brightness     25
Black body radiation     25
Optical aberrations     28
The Seidel aberrations     29
Zero-order aberration     29
First-order aberrations     29
Theorems     35
Aberration coefficients for mirrors     37
The achromatic doublet     39
Fourier transforms: a brief revision     41
Fourier transforms     41
Theorems     42
Convolutions     42
The Wiener-Khinchine theorem     45
Useful functions     45
More theorems     49
Aliasing     51
Physical optics and diffraction     52
Fraunhofer diffraction     52
Two-dimensional apertures and oblique incidence     55
The prism spectrograph     57
Introduction     57
The traditional prism spectrograph     57
The focal curve theorem     59
The Littrow mounting     59
The Pellin-Broca prism     60
Focal isolation     61
The plane grating spectrograph     63
The shape of a monochromatic line spectrum     63
Blazing of gratings     67
Apodising     68
Order overlap and free spectral range     69
Grating ghosts and periodic errors     70
The complete grating equation     72
Differential dispersion     76
Mounting configurations     76
The concave grating spectrograph     89
The Rowland grating     89
The concave grating as a spectrograph     92
The concave grating as a monochromator     96
The aberrations of the Rowland grating     97
Practical details of design     98
The interference spectrograph     101
The phase angle      101
The Fabry-Perot etalon spectrograph     102
Fabry-Perot theory     102
The Fabry-Perot monochromator     104
The Fabry-Perot CCD spectrograph     108
Fore-optics     110
Reference fringes     111
Extraction of the spectrum     111
Choice of the resolution and gap     112
The 'crossed' Fabry-Perot spectrograph     113
The multiplex spectrometer     114
The principles of Fourier spectrometry     114
The multiplex advantage     117
Detectors     120
Silver halide photography     121
Elementary electronic detectors     122
Detectors with spatial resolution     123
Exposure limitations     124
CCD software     125
CCD calibration     126
Spectrograph calibration     126
Auxiliary optics     128
Fore-optics     128
The astronomical telescope as fore-optics     130
Focal reducers     132
Schmidt-camera spectrography     134
Scattered light and baffling     134
Absorption cells     136
Fibre optical input      137
Optical design     139
First steps     139
Initial layout     139
The drawing board     140
Computer ray tracing     140
Refinement of the optical design     141
Requirements of a ray-tracing program     144
Mechanical design and construction     150
The optical layout     150
Optical materials     162
Transparent optical materials     163
Reflectors     163
Metals for construction     165
Other materials     167
Calibration     168
Sensitivity calibration     168
Wavelength calibration     169
Small spectral shifts and radial-velocity measurement     170
Absorption measurements     170
The alignment of a spectrograph     172
The optical alignment     172
The focus     173
Optical aberrations     175
Wavelengths of spectral lines for calibration     179
The evolution of a Fabry-Perot interference spectrograph     183
The common calibration curve in silver halide spectrophotometry     186
Bibliography     187
Index     188