Like last night, there was plenty of cloud cover to contend with from the
same weak weather system, especially
during the first half of the night. Only during the last two hours did
the sky completely clear. Nonetheless, it was another good night for
nearly continuous monitoring of Mrk421 during its incredible VHE outburst.
The clouds were rarely too thick to prevent accurate polarimetry of this
object and nearly the entire night was spent observing Mrk421. The seeing
varied between 1.3-2 arcsec.