Performance characteristics of the new keck observatory echelle spectrograph and imager

摘要

The Echelle SPectrograph and Imager (ESI) is a multipurpose instrument which has been delivered by the Instrument Develpment Laboratory opf Lick Observatory for use at the Cassegrain focus of the keck II telescope. ESI saw first light on august 29, 1999. The optical performance of the instrument has been measured using artificial calibration sources and starlight. Measurements of the average image FWHM in echelle mode are 22 microns (0.22 arcseconds), 16 to 18 microns (0.16 to 0.18 arcseconds) in borad band imaging mode, and comparable in the low-dispersion prismatic mode (LDP). Images on the sky, under best seeing conditions show FWHM sizes of 34 microns (0.34 arcseconds). Maximum efficienies are measured to be 30