VLT SCIENCE PERFORMANCE

LA SILLA PROTOTYPE LINE OF SIGHT SKY ABSORBTION MONITOR (LOSSAM)

A new service is beeing prepared for La Silla visiting astronomers: an online information about the atmospheric absorbtion in the visible. Scheduled for operation in the first quarter of 1996, this is a prototype for the VLT Astronomical Site Monitor.

First Results of the Line Of Sight Sky Absorbtion Monitor over 10 consecutive nights. The progressive arrival of clouds is clearly visible

For this purpose, the La Silla DIMM (Differential Image Motion Monitor) operation has been slightly modified: after each seeing measurement, the finder CCD is used in standard aperture photometry mode to monitor the average flux of the bright star used for seeing measurements.
ESO REVIEW 1996 ..................WP017.........Astronomical Site Testing