On the Stability of Cassegrain Spectrographs'

Gravity-induced flexure has been a long-standing challenge in Cassegrain
spectrographs at 4-m class telescopes; it is more so on the scale of 8-m telescopes.
This is of particular concern for the Gemini High Resolution Optical Spectrograph,
which will be Cassegrain-mounted for its routine mode of operation. In this paper
we address the general flexure problem and make specific recommendations. In a
companion paper we present results on experimental compensation for flexure in a
specific Cassegrain spectrograph - ISIS on the 4.2-m William Herschel Telescope
(WHT).