  At the University of California's Lick Observatory, we have implemented an
on-sky testbed for next-generation adaptive optics (AO) technologies. The
Visible-Light Laser Guidestar Experiments instrument (ViLLaGEs) includes
visible-light AO, a micro-electro-mechanical-systems (MEMS) deformable mirror,
and open-loop control of said MEMS on the 1-meter Nickel telescope at Mt.
Hamilton. In this paper we evaluate the performance of ViLLaGEs in open- and
closed-loop control, finding that both control methods give equivalent Strehl
ratios of up to ~ 7% in I-band and similar rejection of temporal power.
Therefore, we find that open-loop control of MEMS on-sky is as effective as
closed-loop control. Furthermore, after operating the system for three years,
we find MEMS technology to function well in the observatory environment. We
construct an error budget for the system, accounting for 130 nm of wavefront
error out of 190 nm error in the science-camera PSFs. We find that the dominant
known term is internal static error, and that the known contributions to the
error budget from open-loop control (MEMS model, position repeatability,
hysteresis, and WFS linearity) are negligible.
