From their website:
The Piscataquis Heritage Hot Air Balloon Festival is a community driven annual celebration of local talent in arts, trades, crafts, agriculture, non-profit organizations, and the opportunities available in the Maine Highlands Region. This festival, founded by the Kiwanis Club of Dover-Foxcroft and the Piscataquis Chamber of Commerce, is a partnership between businesses and community organizations dedicated to providing an event in the Piscataquis Region, rich in traditional values and full of opportunities to share our heritage with the goal of stimulating the local economy.
In addition to hot air balloons, there will be food vendors (these are all nonprofit organizations), artisans, tradesmen, trades demonstrations, agricultural displays and sales.
There will be entertainment throughout the event along with balloon rides as well as tethered balloon rides for the less adventurous.
Balloon liftoff at 6PM and Balloon glow in the evenings between 8 and 9 PM.
(Admission to the event is $2.00 per person and kids under 3 are free.)
This will be a fun event to walk around, get crowd shots, enjoy the vendors and entertainment, and of course shoot images of the balloon inflation, lift-off, and glow. I put the start time as the beginning of the day's schedule (gates open at 11). I'm local to the event so I'll be there all day either way. If you only plan on part of the day, I'd recommend the latter half (for the balloons).