[ ESO ] La Silla

La Silla - Science Operation Department
Overview of the CES

The CES - truly high resolution!

The CES is ESO's highest resolution spectrograph providing a resolving power of 220,000 in the 346 - 1028 nm region. It is fed through an optical fiber mounted at the f/8 Cassegrain focus. The diameter of the fiber is 2" on the sky. No additional fiber for sky subtraction is available, but for very high resolution spectroscopy of relatively bright targets (> 11 mag) sky subtraction is usually unimportant.

Only a part of one spectral order can be recorded at a time on the CCD, giving a typical spectral range of 2.5 - 6.5 nm. In order to optimize efficiency over the whole range, two instrument paths can be selected:
  • The BLUE path is used at wavelengths below 502.5 nm
  • The RED path is used at wavelengths above 502.5 nm
Observers should note that path changes during the night are not regularly offered. Only in very exceptional circumstances will an effort be made to support them. Path changes will lead to a substantial loss of resolving power (up to a factor 2) due to spectral line tilt and loss of instrument focus.

The Cassegrain fiber adapter (HCFA) also hosts HARPS, which makes it possible to switch between the two instruments with minimal overhead. Complete overhead for a changeover is less than one minute.

Up-to-date information and documentation on the instrument are available on the CES web page at http://www.eso.org/lasilla/sciops/3p6/ces/

Publications based on data obtained with the CES instrument should quote the following reference paper: Enard, D. 1982, SPIE 331, 232

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