Dozens of plein air artists descended on Gloucester’s Main Street on Saturday morning for the Plein Air Invitational, part of this month’s Gloucester Arts Festival. The artists set up around the Gloucester Court House area, including a few in the court circle itself, like Karen Thuermer (above) who painted a picture of the Clayton Building. On Tuesday, plein air artists went to various locations in Mathews, with a reception held that evening at the Bay School Community Arts Center.