  A prototype cross-dispersed optical echelle spectrograph of very high
resolution has been designed and built at Steward Observatory and tested at the
Starfire Optical Range (SOR) 1.5 m telescope. It is the first spectrograph to
take advantage of diffraction-limited images provided by adaptive optics in
order to achieve a potential resolving power of $R \sim 600,000$. The
wavelength coverage in a single exposure is about 300 \AA, which is
approximately 100 times that of conventional spectrographs operating at
comparable resolution. This was achieved by recording 60 cross-dispersed orders
across the $18\times 18$ mm$^2$ area of the CCD detector. The total efficiency
of the system, including the sky and telescope transmission, spectrograph and
CCD detector, is measured to be 1.3% at peak, much higher than that of other
ultra-high-resolution spectrographs. Sample stellar spectra with $R \sim
250,000$ are presented.
