Visible near-diffraction limited lucky imaging with full-sky laser assisted adaptive optics

摘要

Both lucky imaging techniques and adaptive optics require natural guidestars, limiting sky coverage, even when laser guide stars are used. Luckyimaging techniques become less successful on larger telescopes unless adaptiveoptics is used, as the fraction of images obtained with well behaved turbulenceacross the whole telescope pupil becomes vanishingly small. Here, we introduce a technique combining lucky imaging techniques withtomographic laser guide star adaptive optics systems on large telescopes. Thistechnique does not require any natural guide star for the adaptive optics, andhence offers full sky-coverage adaptive optics correction. In addition, weintroduce a new method for lucky image selection based on residual wavefrontphase measurements from the adaptive optics wavefront sensors. We perform Monte-Carlo modelling of this technique, and demonstrate I-bandStrehl ratios of up to 35% in 0.7~arcsecond mean seeing conditions with 0.5~mdeformable mirror pitch and full adaptive optics sky-coverage. We show thatthis technique is suitable for use with lucky imaging reference stars as faintas Magnitude 18, and fainter if more advanced image selection and centringtechniques are used.