It was an agglomeration of the absurd with a dash of arcane astronomical fright. With delirious deliberation - in fact, with four years of planning for the astronomical ''happening'' - several hundred young Baltimorians succumbed Tuesday night to an epidemic of temporary lunacy at an all-night party in a Charles Street bookstore and bar.

Going calculatedly unheeded was all the scientific skepticism about the impact of the syzygy, which is astronomer talk for the unusual assemblage of all nine planets and the Moon on the same side of the Sun. (There were mild tremors in Peru and in the Aegean today, but none of the cataclysms predicted by the superstitious as the planets clustered closer together than at any time in 179 years.)

While the civic boosters of this city's Greater Baltimore Committee slept under the full moon, the partying ''Krononauts,'' or travelers in time, gathered under the auspices of the Crater Baltimore Committee to christen a hitherto unnamed Moon hole ''Baltimore.'' They assembled Tuesday night under a huge photographic enlargement of the ''Crater Baltimore'' to await the arrival of ''visitors from the futures'' as the planets moved into alignment.

''There is more than one future,'' said Kirby Malone, 27 years old, who is one of the operators of the Empire Salon, a gallery of ''the performance arts'' in the Second Story Bookstore at Charles and Centre Streets. He was wearing a white shirt and tie and white duck trousers, painstakingly speckled with exclamation points in bold strokes of a black felt-tipped pen, which, he explained, ''is writing for people from the futures who don't speak English.''