eso0027-en-us — Organisation Release
"First Light" Approaches for Fourth VLT Unit Telescope
YEPUN's Secondary Mirror Now in Place
28 August 2000
These days, the ESO staff at Paranal is having a strong feeling of "déja-vu". Only seven months after the third 8.2-metre VLT Unit Telescope, MELIPAL, achieved "First Light", this crucial moment is now rapidly approaching for YEPUN , the fourth and last of the giants at the ESO observatory.
Following successful coating with a thin layer of aluminium in early June 2000, the 8.2-metre primary Zerodur mirror (M1) was placed in its supporting cell and safely attached to the mechanical structure of YEPUN on July 31.
On August 26, the 1.1-metre M2 Beryllium Mirror for YEPUN was coated. Again, this delicate operation went very well and the measured reflectivity was excellent, about 91%. The M2 mirror and its support were then assembled and successfully installed at the telescope on Sunday, August 27.
Before the optical mirrors were installed, and with dummies in their place, careful tests were made of most telescope functions. In particular, this included accurate balancing of the 450-tonnes telescope frame on its hydrostatic oil bearings, as well as precise adjustment of all motions. It now remains for the ESO engineers to do the final performance optimization of the entire telescope.
The work on the fourth telescope has been particularly noticeable because a large proportion of the assembly, integration, tuning and testing was organised and executed by ESOs young group of capable engineers and technicians. As the engineering staff at Paranal has grown and during the earlier work on the first three telescopes, they have been acquiring the necessary expertise to autonomously integrate and maintain the 8.2-metre telescopes.
During the coming "First Light" observations, light from the selected celestial objects will be registered by the VLT Test Camera at the Cassegrain Focus. This comparatively simple instrument was also used for the consecutive "First Light" events for ANTU (May 1998), KUEYEN (March 1999) and MELIPAL (January 2000). It is mounted on the telescope's optical axis within the M1 Mirror Cell, just behind the main mirror.
It is planned to make one or more of these first images available on the web soon thereafter.