An experience that eclipses all

THE temperature drops, the day darkens and dots of sunlight turn into crescents on the ground, light on pale colors rippling as if reflected through a swimming pool. Then the moon fully obscures the sun, which appears to be a black dot in the sky surrounded by a diaphanous halo. Everyone cheers.

In the world of fabulous travel experiences, watching a total solar eclipse has little competition. One occurs about every 18 months.

A solar eclipse happens when the sun, moon and Earth line up, and the moon’s shadow falls on Earth.

The path of totality, where the moon’s full shadow crosses Earth, is about 100 miles wide. The shadow moves at more than 2,000 mph, so an eclipse can be seen in one spot for only seconds or minutes. Eclipso-philes -- people like me who chase eclipses around the planet -- try to be at the shadow’s center, where the eclipse lasts the longest.

The next total solar eclipse -- March 29 -- will travel over parts of northeastern Brazil, western Africa, Libya (where getting visas has been difficult), Egypt, Turkey, Kazakhstan, Russia and Mongolia. It will last the longest -- just more than four minutes -- near the border of Chad and Libya, and more than 3 1/2 minutes in the rest of Africa and Turkey.

Although time is growing short, some companies have space on tours timed to the March 29 eclipse. Among them:

* Twilight Tours: 10-day trip to Turkey, March 25-April 2, from $2,975 per person, double occupancy. Information: (818) 575-9580, www.sciencecenter.net/twilighttours.

* Astronomical Tours: limited availability on 11- and 12-day tours to Niger for $2,495 to $2,695 per person double occupancy, March 29 to April 4 and March 21 to April 1. Information: (888) 734-0311, astronomicaltours.net.

* Winco Eclipse Tours: 11-night trip to Egypt for $4,253, March 19 to 30. Information: (617) 630-0280, www.wincoeclipsetours.com.

* MWT Associates: 12-day trip to Turkey for $3,695 per person, double occupancy March 21 to April 1. Information: (877) 707-7827, www.melitatrips.com.

* SITA World Travel: 10-day tours to Turkey for $1,590 per person, double occupancy, from March 22 to 31, and eight-day tours to Libya from $2,700, March 25 to April 1. Information: (800) 421-5643, www.eclipsetours.net.

If you miss this eclipse, there’s time to catch the next one on Aug. 1, 2008, in northern Canada, Greenland, Siberia, Mongolia or China.

One tip: Be sure you’re going to a total solar eclipse. Even 99% of totality (with the moon covering 99% of the sun) doesn’t compare with a total solar eclipse.