Testing the limit of AO for ELTs: diffraction limited astronomy in the red optical

M. Tecza, J. Magorrian, N. Thatte & F. Clarke
Many of the proposed science cases for extremely large telescopes (ELT) are only possible because of the unprecedented sensitivity and spatial resolution due to advanced, e.g. tomographic and multi conjugate, adaptive optic (AO) systems. Current AO systems on 8-10m telescopes work best at wavelengths longward of 1 micro-m with Strehl ratios >= 15 per cent. At red-optical wavelengths, e.g. in the I band (0:8 micro-m), the Strehl ratio is at best a few percent. The...