<title>User interface and control software for the HIRES image rotator on Keck-1</title>

Abstract

We describe the control and user interface software for the image rotator on the high resolution echelle spectrometer (HIRES), located at the Nasmyth focus of the Keck-1 10-meter Telescope. This image rotator counteracts the field rotation induced by the alt-az telescope mount and aligns the image delivered to the spectrometer slit and the slit-viewing TV camera. The rotator can align the image so that either a specified position angle on the sky or the atmospheric dispersion vector is held fixed relative to the slit. The rotator is physically an integral part of the spectrometer; but, since it affects telescope pointing and auto-guiding, it can also be considered part of the telescope. Accordingly, it interacts with the control systems for both the telescope and spectrometer. The apportionment of rotator control functions between these two systems poses interesting operational challenges. Since the telescope operator and the observer each need to operate the rotator at various times, their respective user interfaces must provide consistent rotator control and status functions.