"Periscope" is a set of lessons to support learning assistants, teaching assistants, and faculty in learning to notice and interpret classroom events the way an accomplished teacher does. "Periscope" lessons are centered on video episodes from a variety of best-practices university physics classrooms. By observing, discussing, and reflecting on teaching situations similar to their own, instructors practice applying lessons learned about teaching to actual teaching situations and develop their pedagogical content knowledge. Instructors also get a view of other institutions' transformed courses, which can support and expand the vision of their own instructional improvement and support the transfer of course developments among faculty. "Periscope" is available for free to educators at http://physport.org/periscope.