Five Hundred Fools stood freezing their feet off in the snow in the dark by an obscure highway Monday morning, every one of them as happy as a swilled hog in the sunshine. The eclipse groupies were in totality, which is to say that the moon's shadow had completely blocked out the sun, producing a total solar eclipse, the most spectacular of all celestial events.

The eclipsies, also known as eclipse junkies, freaks and buffs, are, in the aggregate, as mild, intelligent and civilized a bunch of monomaniacs as one can find. The have the eccentric charm of those who are devoted to other harmless passions such as bird watching, philately and Jane Austen. When extremely vexed, they are apt to lapse into strong language, such as "Oh, the dickens."

They had paid $385 a head, this group of 500, to witness two minutes and seven seconds worth of what is, in truth, an absolutely awesome phenomenon. They had come from as far as Puerto Rico and Mexico, armed with telescopes, tripods and enough exotic camera equipment to produce a bull market in Kodak stock. They had spent three days at the Big Sky resort in Montana's beautiful Madison mountain range, resolutely ignoring the siren call of the ski slopes in favor of lectures on solar physics and meteorology.

The eclipsies took over Huntley Lodge, named after Chet Huntley, the late television newsman and developer of Big Sky. The normal cheer of aprés ski, with its crowded bars and macho-ridden tales of monster moguls conquered, gave way to earnest discussions of sunspots, Bailey's beads and what was likely to be going on in the corona during totality.

For Phil and Marcy Sigler of New York City, organizers of the expedition and the foremost eclipse impresarios of the Western world, it was the sixth voyage to darkness. In real life, Mr. Sigler is a somewhat antic teacher of sociology at the City University of New York. Mrs. Sigler, a small, striking brunette of Greek descent, was once described in a limerick by Isaac Asimov, the popularizing polymath, as "the unique Greek with the chic physique". Mr Asimov was aboard during one of the Sigler-organized eclipse voyages, on which determined eclipsies charter whole ocean liners to track the elusive totality.

Well over half the eclipsies at Big Sky were veterans of previous voyages to darkness, which gave the gathering something of the air of a family reunion.

The key to a successful eclipse expedition, according to Mr. Sigler, is mobility. The greatest dread of all eclipsies is being "clouded out," which is the equivalent of having your opponent score 28 points in the first quarter. In order to fully appreciate an eclipse, it is first necessary to be able to see the sun, for which useful purpose the Siglers enlist the services of Dr. Edward Brooks, a meteorologist at Boston College. Dr. Brooks's specialty is finding holes in the clouds, and he employed the ancillary services of the Government weather intelligence, a network of ham radio operators and Scott Carpenter, the former astronaut and aquanaut and current eclipse junkie, who spent Tuesday morning flying around eastern Montana in a small jet. Mr. Carpenter currently lives in California and is involved in a business concern.

At 2 A.M. Monday, all 500 eclipsies filed aboard 15 chartered buses and took off for a destination somewhere between Lewiston and Round Up, depending on the clouds. Six and a half hours later, they debarked west of Lavina to create an instant half-mile forest of tripods, much to the bemusement of local ranchers who drove by.

As the moon shadow started to bite into the sun, Dr. Frank Robertson of St. Louis was exalted. "It is the most wonderful thing I have ever seen," he declared. "I tell you, ever since I was a kid I have wanted to see a solar eclipse. One of my life's ambitions has been realized. Goll-lee!"

Herman Carus of Peru, Ill., was less excited, as befits a more experienced eclipsie. Mr. Carus turned 80 on Tuesday. His party included his brother Alwin, who has been watching eclipses since 1918, his wife, his sister, a grandson, his wife's niece and her sister-in-law.

Two of the most faithful eclipsies are Marge Nicol and Isabelle Mackerracher of, respectively, Milburn, N.J., and Wellesley, Mass. They were the very first to sign up for the first voyage to darkness in 1972. They are cousins who always dress identically, ladies of a certain age who are indefatigable world travelers.

On that first voyage, they booked an extra room for Penny, Marge Nicol's cat (making her Penny Nicol, you see.) Penny, a silver-white Persian, always went along on the cousins' travels and for years their Christmas cards were photographs of Penny — Penny on a gondola in Venice, Penny on a camel by the Egyptian pyramids, Penny looking out her porthole window at the eclipse. Penny, alas, has passed on, but Marge and Isabella perservere. Since the last eclipse in 1977, they have been up the Amazon River and down the Galápagos Islands.

The eclipsies come from all walks of life, and this year's sampling included a welder from Michigan, a psychiatrist from Los Angeles and a television engineer from Wisconsin. Many of them are amateur astronomers and find out about organized eclipse-watching tours through their local planetariums or such magazines as Sky and Telescope, and Natural History.

As they waited in the snow west of Lavina, they presented an extraordinary motley of fashion. One fellow wore a jumpsuit of safety orange while a woman complemented her full-length fur coat with Arctic explorer boots. "Dark, dark, dark," they chanted, "come on dark." A hot-air balloon threatened to interfere with their view of the eclipse just three minutes before totality. "Shoot it down," shouted the ruthless eclipsies. "Does Scott Carpenter have anti-aircraft guns on his jet?" Happily, the balloon sailed on before mayhem became necessary.

At last the dark came, sweeping out of the Western mountains at 1,000 miles an hour. The tripod forest became hushed, bathed in an eerie dark, sudden and complete, for all the world another planet. Overhead, Venus glowed in the sky and the sun was gone, leaving for a moment a brilliant diamond ring and then a fantastic, glowing corona, the plumes and petals of the sun, spitting traces of red, pink, purple, chartreuse and orange.

It was, the eclipsies agreed, the shortest two minutes, seven seconds any of them had ever spent. "Fantastic" was the word of choice. Jessie Jackson of Los Altos Hills, Calif., said, "This is my second eclipse and you can bet I'll do it again. The next one in this country is in 2017 and I'll be 95 years-old and I'm going to make it. I may not be able to see it, but I'll be out for it."

Howard Dash and Harvey Wachtel of New York City appeared higher than kites with the wonder of it all. "I just love beautiful things,"said Mr. Dash, explaining his presence on the edge of a Montana highway.

The dark moved on, leaving only a splotch to the east in the suddenly pedestrian countryside. An Eddie's Bread truck drove by and a peripatetic jogger came along. The eclipsies got back aboard the buses, their heads full of brilliant diamond rings and fantastic coronas. They were, one and all, ready for the next eclipse.