Adaptive Optics for Small Aperture Telescopes

Abstract

Adaptive Optics (AO) is one of the techniques to reduce aberrations caused by atmosphere turbulence in the light coming from objects above this layer that reaches ground based optical telescopes. It was proposed 62 years ago, and since then it has undergone a fast evolution due to the technical developments in mechanics, optics and electronics. Due to these advances and the efforts of the research community, AO nowadays is widely used in big and moderate size telescopes and it has become an essential instrument in this telescope segment.

The research for its use in small aperture telescopes has been limited for different factors: it is an expensive technique; small aperture involves less gathered light that could reduce AO performance; and also low altitudes where usually these telescopes are located result in severe aberrations. This research has been focused in the investigation of new techniques and procedures that facilitate the engineering of an AO system for small aperture telescopes.

For this purpose an AO testbed has been developed, which includes a portable opto-mechanical platform adapted specifically for its use in small aperture telescopes, which has been tested in laboratory and assessed with on-sky experiments.

In this research, an original AO real time processing control architecture has been defined, that can be fully implemented in a low cost standalone Field Programmable Gate Array (FPGA) device, unlike standard AO configurations, which typically rely in complex distributed hardware architectures which make the system more expensive and less portable.

The lack of gathered light inherent to small aperture telescopes constitutes a severe limitation for an AO system. Hence is crucial to develop optimized image processing algorithms that balance this drawback. Here a novel fast implementation of a centroiding algorithm has been accomplished, adapted to severe low light conditions, and from this a closed loop AO system has been demonstrated.

There is wide potential demand in the scientific and amateur astronomy community in this field, and the innovations and engineering concepts introduced here constitute a valid and proven AO system applied for small aperture telescopes.