The general equations for parameters of concave grating mounts that pr
ovide stationary and superstationary astigmatism at the wavelength of
correction are derived for the first time, to the best of our knowledg
e. These can be used to design grating multi/demultiplexers for wavele
ngth-division multiplexed optical communication systems and high-resol
ution, narrow-band spectrographs. Important special cases of stationar
y anastigmatic mounts and their performance are presented. (C) 1997 Op
tical Society of America.