Crisp, beautiful late fall day, clearing by 10 am, sunny, low 50s F, light W and NW winds up to 10 mph. Lots and lots of 'cyclists out there today (Saturday), both bicyclists and motorcyclists. I was the last bicyclist for the day to climb up the summit road (now closed --prob. since Oct 31-- to motor vehicle traffic, until next May), but there were many hikers coming down the trails and summit road. Departed the summit at exactly 4:00 pm, saw sunset at 4:20 pm descending Mountain Rd just before Princeton Ctr (~1275 ft elev). Visibility: on climb up, Boston skyline just barely visible from Princeton Ctr. junction of Rts 31 and 62, but 45 min. later, no longer visible from summit. Today at sunset, lighting of distant mountains and horizon had that look that reminded me of a seashore type visibility produced by all of the salt particles and water drops in the air. Greater Boston Glider Club operations were ongoing but rapping up at the Sterling Airport when I passed by and stopped for 15 min. at ~2:30 pm, chatting w/ a couple of club members who were also bike enthusiasts. Saw one glass ship scratching for lift just to the E of airport, eventually coming in for a landing.