The 11th GEOS Symposium was held in Marly‑le‑Roi from 1 to 3 April 1988, marking the return of the congress to France after the previous general meeting organized in Las Fuentes (Spain) in September 1986. The event brought together around forty observers.
Work on V2203 Oph revealed a systematic shift of the minima compared with Surikov’s ephemeris, making it necessary to resume observations. A review of several suspected variables made it possible to confirm or refine their classification thanks to visual and photoelectric observations.
The campaigns carried out at the Pic du Midi and the Jungfraujoch produced significant results, including the reclassification of two stars initially considered RR Lyrae, as well as the photometric characterization of NSV 4285 Cnc and RR VI‑51 Lyn. The 1987 Italian summer camp provided data on BK Dra, CY Aqr, and CV Dra.
A study of ρ Persei highlighted probable multiperiodicity and confirmed the consistency between visual estimates and photoelectric measurements. Analyses of EW Sct recovered the two frequencies previously identified visually.
A structuring debate focused on the organization of photoelectric photometry within GEOS. Since the Las Fuentes meeting, the situation had evolved, leading the assembly to decide on the suppression of the photoelectric section, replaced by a system of technical coordinators.
Finally, a general reorganization of GEOS was adopted: the merging of several sections, the suppression of the “asteroidal occultations” section, new rules for monthly submissions, and an update of the observation program.