Introduction

The purpose of this chapter is to describe the Optopus package, the set of programs, now implemented in MIDAS, which helps the Optopus observers to prepare their observations in a fast and easy way.

The Optopus facility is designed to enable conventional use of the Boller and Chivens spectrograph to be extended to perform spectroscopy of multiple or large extended objects simultaneously (see G. Lund, 1986, OPTOPUS, ESO Operating Manual No. 6, for further details). At present, Optopus is available for use at the 3.6m telescope only.

The fibre component of Optopus consists of 54 separately cabled optical fibres which enable light to be guided from freely distributed points in the focal plane at the entrance slit of the spectograph. The fibre ends are precisely located at the telescope focal plane by means of accurately drilled templates, known as ``starplates''.

The Optopus starplates (one for each observed field) are prepared in an automatic process in the ESO workshop on La Silla, after the observer has produced a drilling instruction file from his/her coordinate dat for each field. The Optopus package in MIDAS enables Optopus observers to create the file with the instuctions for the computer-controlled milling machine. It has been designed to be as ``user friendly'' as possible. All the commands request a minimum amount of input from the user; in addition they verify use of correct parameters.

Please do not forget that the instruction file has to be transferred to La Silla. Also, note that the milling machine on the mountain can only produce 2 to 3 starplates per day. If in doubt, always check with the Visiting Astronomers Section at ESO Headquarters in Garching at least three months prior to the observations.