  Vibrations are a key source of image degradation in ground-based
instrumentation, especially for high-contrast imaging instruments. Vibrations
reduce the quality of the correction provided by the adaptive optics system,
blurring the science image and reducing the sensitivity of most science
modules. We studied vibrations using the Subaru Coronagraphic Extreme Adaptive
Optics (SCExAO) instrument at the Subaru Telescope as it is the most vibration
sensitive system installed on the telescope. We observed vibrations for all
targets, usually at low frequency, below 10 Hz. Using accelerometers on the
telescope, we confirmed that these vibrations were introduced by the telescope
itself, and not the instrument. It was determined that they were related to the
pitch of the encoders of the telescope drive system, both in altitude and
azimuth, with frequencies evolving proportionally to the rotational speed of
the telescope. Another strong vibration was found in the altitude axis of the
telescope, around the time of transit of the target, when the altitude rotation
speed is below 0.12 arcsec/s. These vibrations are amplified by the 10-Hz
control loop of the telescope, especially in a region between 4 and 6 Hz. In
this work, we demonstrate an accurate characterization of the frequencies of
the telescope vibrations using only the coordinates -right ascension and
declination- of the target, and provide a means by which we can predict them
for any telescope pointing. This will be a powerful tool that can be used by
more advanced wavefront control algorithms, especially predictive control, that
uses informations about the disturbance to calculate the best correction.
