Getting Lucky with Adaptive Optics: Fast AO Image Selection in the Visible with a Large Telescope

TL;DR

This paper presents a new instrument combining Lucky Imaging and Adaptive Optics that achieves routine diffraction-limited imaging in the visible spectrum on a 5m telescope, demonstrating significant resolution improvements under typical conditions.

Contribution

The paper introduces a novel system that integrates Lucky Imaging with adaptive optics for the first time to routinely produce diffraction-limited images in the visible spectrum on a large telescope.

Findings

Achieved Strehl ratios of 5-20% at 700 nm with median 12%.

Obtained diffraction-limited resolution of 35 milliarcseconds at 700 nm.

Demonstrated wide-field imaging with 300 milliarcsecond resolution over 30x30 arcsec.

Abstract

We describe the results from a new instrument which combines Lucky Imaging and Adaptive Optics to give the first routine direct diffraction-limited imaging in the visible on a 5m telescope. With fast image selection behind the Palomar AO system we obtained Strehl ratios of 5-20% at 700 nm in a typical range of seeing conditions, with a median Strehl of approximately 12% when 10% of the input frames are selected. At wavelengths around 700 nm the system gave diffraction-limited 35 milliarcsecond FWHMs. At 950 nm the output Strehl ratio was as high as 36% and at 500 nm the FWHM resolution was as small as 42 milliarcseconds, with a low Strehl ratio but resolution improved by factor of ~20 compared to the prevailing seeing. To obtain wider fields we also used multiple Lucky-Imaging guide stars in a configuration similar to a ground layer adaptive optics system. With eight guide stars but very undersampled data we obtained 300 milliarcsecond resolution across a 30X30 arcsec field of view in i' band.