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We will describe in this chapter the seeing effects of the turbulence found in the immediate vicinity of the telescope, namely that generated by the enclosure, the telescope itself and in the ground surface layer (up to about 30 50 m).
Until a few years ago, the different 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 scarce and episodic, also because of the objective difficulty in devising and interpreting valid experiments.
Citing [Woolf 82] "... [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 and this chapter intends to provides a description, interpretation and parameterisation of the main local seeing effects. These can be separated in different types: