Auxiliary full-disc telescope for the European Solar Telescope

Abstract

The Auxiliary Full-Disc Telescope (AFDT) will be used for the orientation of the observer on the solar disc and in its surroundings, for an easy guidance of the European Solar Telescope (EST) to a selected target, and for precise coordinate measurements. AFDT can be used as an autonomous robotic telescope for synoptic observations and records of solar activity also when no observations are carried out at the EST main telescope. The principal functions of AFDT and the related requirements are summarised. The specific axial mechanical structure accommodating the refractor optical system is outlined. The optical system and its components are described. Two alternatives of the positional control system - the active guiding system and the passive guiding system - are described and their functionality is analysed.