The display was set up on the battlefield, around the full-scale wooden fortress wall that was built two years ago by volunteers. Setup began at about 10:00 a.m. and took nearly twelve hours, in addition to the planning work that occurred before the crew arrived. A Pennsic staff member with modern-world firefighting experience stood by the entire day, to ensure that an accidental match or cigarette dropped by a passing observer would not cause an accident.
The fireworks were electrically triggered, which is of course not period, but Cartwright Fireworks claims that most of the devices used are modern variants of period pyrotechnic charges.
A large percentage of the Pennsic populace of about twelve thousand turned out for the display, and cheers could be heard from all the way across the 700-acre Cooper's Lake site.
The link from the headline above goes to a photo album provided by Iustinos Tekton called Justin. The author and photographer's main home page is at http://4th.com/sca/justin/ .
There is another photo album online at pennsic.net, from Arwen ferch Morgan, at http://www.pennsic.net/cgi-bin/pennsic/photos03.cgi?cat=amanda .