  To perform imaging observation of optically red objects such as high redshift
quasars and brown dwarfs, the Center for the Exploration of the Origin of the
Universe (CEOU) recently developed an optical CCD camera, Camera for QUasars in
EArly uNiverse(CQUEAN), which is sensitive at 0.7-1.1 um. To enable
observations with long exposures, we developed an auto-guiding system for
CQUEAN. This system consists of an off-axis mirror, a baffle, a CCD camera, a
motor and a differential decelerator. To increase the number of available
guiding stars, we designed a rotating mechanism for the off-axis guiding
camera. The guiding field can be scanned along the 10 acrmin ring offset from
the optical axis of the telescope. Combined with the auto-guiding software of
the McDonald Observatory, we confirmed that a stable image can be obtained with
an exposure time as long as 1200 seconds.
