DETAILS: Mount Washington Observatory

Overnight visits at the Mount Washington Observatory run through mid-April this season. (The schedule for 2008-09 will be available in late summer.) Trips leave from the base of Mount Washington at 8:30 a.m. on the first day of the two-day trip, then head back to the valley the next afternoon (weather permitting). The trip includes transportation, lectures and field trips, tours of the observatory and the summit, all meals and overnight lodging.

Sleeping arrangements are summer camp style, with bunk beds and a shared bathroom. There is heat, but no showers for guests.

The EduTrip program is open to members of the observatory, and most participants join just to make the trip. In addition to the membership fee ($30 and up), the cost of each trip is $459 per person. Any "physically fit" adult can make the trip, as can teenagers 14 and older who are accompanied by a parent or guardian.

Because of the fast-changing weather on the mountain, trips sometimes are canceled at the last moment. If that happens, you get a refund, and your trip will be rescheduled if possible. A storm can hit after you've reached the top, meaning your trip back down can just as easily be delayed.

So it's wise to keep your calendar clear for a day or two after your trip is supposed to finish. The observatory requires at least five participants for a trip to take place.

GETTING THERE: Mount Washington is in north-central New Hampshire, about a 3 1/2 -hour drive north of Boston. The closest major airports are in Manchester, N.H., and Portland, Maine. Sale fares on Southwest for nonstop flights from Baltimore to Manchester go as low as $129 round trip. AirTran offers sale fares starting at $155 round trip for nonstop flights from BWI to Portland. United has nonstop flights from Dulles, and US Airways offers nonstop service from Reagan National to both airports, but round-trip prices start at about $400.

If you're driving from Washington (about an 11-hour drive), take Interstate 95 north and take the "U.S. 4/Route 16/Spaulding Turnpike" exit (Exit 4) toward "N.H. Lakes/White Mountains." Merge onto New Hampshire Route 16 north.

GEAR: Required equipment includes insulated boots, ski goggles, insulated mittens, a sleeping bag rated for 32 degrees or colder, an ice ax or ski pole, and crampons (which the observatory sometimes can supply). When you arrive, the EduTrip staff will check to be sure you've got the full list of stuff and might turn you away if you don't.

INFORMATION: Mount Washington Observatory, 603-356-2137 or 800-706-0432, http://www.mountwashington.org/education.

-- P.M.