A Universe lit up by one first-magnitude star and not much else. ""Old Folks at Home,"" in which unconquerable 67-year-old Zoe Breedlove joins an experimental ""marriage"" of seven elderly persons, is the latest and among the best in Michael Bishop's remarkable Atlanta series. Other nice contributions are Charles Ott's macabre lampooning of ""The Ecologically Correct House"" and Michael Cassutt's account of emotional consequences in a world where the young can become objectively as well as subjectively immortal. R. A. Lafferty plays with an oddly thin idea about a rediscovered 1870's TV impresario; Greg Bear's middling-good ""Scattershot"" has a host of wildly divergent beings from parallel Earths trapped in an area of ""probability disruption."" Other contributors: Cynthia Felice (telepath wrestling with mind of friend in a coma), Gordon Eklund (artist computer-programmed to relive the career of Jan Vermeer), Gregory Benford (sterile blueprint of a confrontation between technocratic and post-technocratic values). Respectable but lackluster collection.