La Silla - Science Operation Department

CES image slicer diffuse light monitoring

All measurements were done using the saturated (interstellar) NaI D lines (5890 Å and 5896 Å) seen in certain stars. The uncertainties are internal errors estimated from the S/N of the spectrum, and may not reflect the true accuracy of the measurements. Only the high-resolution slicer is monitored. This information is also available in graphical form.

At other wavelengths one must use a different approach, based on measuring equivalent widths (EW) in a solar spectrum obtained with the CES and comparing with a "canonical" solar spectrum. Such monitoring has recently (Jan. 2005) been started, and will eventually replace the use of Na D stars. Below we give the measured scattered light using this method:

Users aiming at measuring accurate equivalent widths should correct their spectra for scattered light, using either the values quoted here, or (better) by estimating the scattered light in Solar Spectra. We are building a database of calibrations from where the relevant data can be downloaded.