  We describe a device (adapter) for off-axis guiding and photometric
calibration of wide-angle spectrographs operating in the prime focus of the 6-m
telescope of the Special Astrophysical Observatory of the Russian Academy of
Sciences. To compensate coma in off-axis star images an achromatic lens
corrector is used, which ensures maintaining image quality (FWHM) at a level of
about 1'' within 15' from the optical axis. The device has two 54'-diameter
movable guiding fields, which can move in 10' x 4'.5 rectangular areas. The
device can perform automatic search for guiding stars, use them to control the
variations of atmospheric transmittance, and focus the telescope during
exposure. The limiting magnitude of potential guiding stars is mR ~17 mag. The
calibration path whose optical arrangement meets the telecentrism condition
allows the spectrograph to be illuminated both by a source of line spectrum (a
He-Ne-Ar filled lamp) and by a source of continuum spectrum. The latter is
usually represented either by a halogen lamp or a set of light-emitting diodes,
which provide illumination of approximately uniform intensity over the
wavelength interval from 350 to 900 nm. The adapter is used for observations
with SCORPIO-2 multimode focal reducer.
