How Ground-Based images help Hubble ST

Hi all,

Attached you have two graphs showing how recent ground-based observations
of Saturn are helping the current HST campaing to track the most
conspicuous features in the atmosphere. In addition to retrieve a precise
rotation period (i. e. zonal velocity), we can constrain their lifetime,
which is important for dynamical studies on the nature of these features.

We urge the IOPW members to make new observations with a recommendation on
filters based on our HST experience. Two type of filters work are enough
to constrast the spots: a blue one (not violet) something similar to the
Johnson B, and a "very red" filter (700-900 nm) where CCDs are most
sensitive. The bright features are well contrasted in both wavelengths,
but the red filter could also show the dark spots (there are many at
different latitudes).

Good observations!