Abstract

The advantages of mirror optics for spectrographic systems are well known, namely, that all wave lengths focus at the same place and that the reflection losses can be made very small. Most modern spectrographs use mirror optics. Some are able to use spherical mirrors while others must use off-axis paraboloidal mirrors to achieve the desired resolution. Inexpensive concave spherical mirrors are ideal for imaging the source on a spectrograph slit, except for the problem of astigmatism. Expensive off-axis corrected mirrors can be obtained, but they must then be used only at the designed off-axis angle. We have found a simple adjustable way to reduce the astigmatism from inexpensive spherical mirrors used at moderate off-axis angles.

Methodology for third-order astigmatism compensation in off-axis spherical reflective systems

Armando Gomez-Vieyra and Daniel Malacara-Hernández
Appl. Opt. 50(7) 1057-1064 (2011)

Geometric theory of wavefront aberrations in an off-axis spherical mirror

Armando Gomez-Vieyra and Daniel Malacara-Hernández
Appl. Opt. 50(1) 66-73 (2011)

Off-Axis Paths in Spherical Mirror Interferometers

D. Herriott, H. Kogelnik, and R. Kompfner
Appl. Opt. 3(4) 523-526 (1964)

Astigmatism-reduced spherical concave grating holographically recorded by a cylindrical wave and a plane wave for Rowland circle mounting

Xinwei Chen and Lijiang Zeng
Appl. Opt. 57(25) 7281-7286 (2018)

Influence and control of spherical aberration in polishing off-axis aspherical mirrors by the stressed method

Jiang Zi Bo, Li Xin Nan, Yu Bin Bin, Zheng Yi, and Li Bo
Appl. Opt. 54(2) 291-298 (2015)