INTRODUCTION

Until a few years ago, the various effects which will be described in this chapter were encompassed under the general term of dome seeing. Although the problem has been well recognized at least since the mid-70s when several new telescopes of 4-m class were commissioned, experimental measurements remained for a long time scarce and episodic, also because of the objective difficulty in devising and interpreting valid experiments.

Citing Woolf[8] in 1982: "... [dome] seeing in telescope design has been treated as a magician treats a rabbit. A number is pulled out of a hat, to great applause, it is handed to an attendant waiting in the wings, and it is seen and thought of no more." The successive decade provided indeed some more data from which it has now been possible to attempt an improved understanding of this phenomenon.

The author presented in 1995 a PhD dissertation[10] , which describes and discusses in a comprehensive manner the issues related to the interaction of a modern telescope with its local atmospheric environment. Several new notions and methods were described which allow a better understanding of the turbulent phenomena occurring near and inside different types of telescope enclosure. The knowledge acquired on these effects is then applied to new procedures for a global evaluation of telescope performance and contributes to the general progress of the engineering of telescope enclosures. The present article presents a summary of the most useful expressions and engineering parameterizations of the various seeing effects.