Stellar bycatch refers to the many stars incidentally captured within a radio telescope’s field of view alongside its primary SETI target — an overlooked source of additional surveyed stars in every observation. louisa-mason’s 2026 ALMA-based study used the Besançon Galactic Model (a stellar population synthesis model) instead of the Gaia catalog to estimate this bycatch population, since Gaia under-counts stars too distant, faint, or crowded to reliably identify. Applied retrospectively to a prior 1,327-pointing SETI survey, the method raised the estimated number of surveyed stars from ~288,000 (Gaia) to over 6.1 million (Besançon model) — suggesting existing SETI archives cover far more of the galaxy than previously credited (src-ras-alien-radio-channel-technosignature-2026-07).