Adapters and beam combination aspects, baffles

Abstract

The term “adapter” is widely used to describe the more or less complex unit which is required at the focus stations of modern telescopes in order to control and operate the telescope. The modern adapter started to evolve when “offset guiding” replaced the old technique of a separate guiding telescope, normally a smaller refracting telescope rigidly attached to the main telescope. With increasing size and precision, this original solution was no longer adequate because of differential flexure problems, above all in the larger instrument. Offset guiding, i.e. guiding on a star image in the field of the main telescope, was a huge advance since only differential field effects caused errors. Of course, in many observing modes where the object is bright enough, guiding is done on the observed object itself or in the small instrument field.