Gemini 8 Meter Telescopes Active Guiding System Considerations

Abstract

The GEMINI telescopes are intended to deliver very good image quality with only tip-tilt correction at the secondary mirror. Designing the guiding systems for these telescopes has made use of simple yet accurate models of the image size. These are described here, with illustrations of the complex tradeoffs that are necessary to achieve the best images. The current design of the guiders is given. These also serve as active optics wavefront sensors to provide closed loop control of the telescope alignment and figure at slow rates.