Design of the tip-tilt mirror for the adaptive optics system of amateur telescopes, and optimum placement of actuators

The recent development of the Adaptive Optics (AO) system for ground based tele­scopes has enabled astronomers to improve the quality of images distorted by atmo­spheric turbulence. The main objective of the present work is to design a tip-tilt AO system for telescopes used by amateur astronomers. Here we have designed the tip­-tilt mirror and its mounting accessories for the tip-tilt adaptive optics system. The three piezoelectric actuators used to create the tip-tilt motion of the mirror, have been placed on a concentric circle in such a way that the distortion of the top surface of the mirror is reduced to a minimum. For the optimum placement of the actuators, a new semi-analytical approach has been used. Here the mirror has been modelled as a thin circular plate with a peripheral ring mass ( equal to the mass of the frame) and an elastic edge support. Modal analysis is performed to determine the natural frequencies and mode shapes of the system. The results of the modal analysis are incorporated in the subsequent harmonic analysis, where the response of the system to harmonic forces applied by the three actuators is expressed in terms of Green functions. For various positions of the actuators the maximum distortions on the mirror surface have been evaluated, and from these results, the optimum positions of the actuators are located. The results of the semi-analytical results are compared with the finite element (FE) results obtained by using ANSYS FE software. The semi-analytical method has been shown to be a very efficient technique in locating the optimum position of the actuators.

Author dc:creator

• Chakraborty, Parthapratim

Statement dc:rights

• Available to the World Wide Web

Handle dc:identifier.uri

https://hdl.handle.net/1828/17413

OAI identifier oai:identifier

oai:dspace.library.uvic.ca:1828/17413