The ninth GEOS International Symposium, held in Marly from 25 to 27 May 1984, was widely regarded as a success. Despite a national railway strike, fifty‑two participants—including forty‑four GEOS members from Italy, France, Belgium, Spain, and Switzerland—were able to attend. The invited professional astronomer, Bernard Nicolet of the Geneva Observatory, presented a clear and instructive analysis of UBV photoelectric photometry, using a (U–B)/(B–V) diagram to illustrate stellar distributions and the effects of interstellar reddening.
Several organizational decisions were made during the meeting. The FT 17 research program was scheduled for a second revision to include new research stars, while the Fr 18 campaign list remained valid in its 1983 form, with no new campaigns planned for 1984. A new FT document would also define a “recommended program” of selected r, P, and To stars for which GEOS charts would be produced. Observers were invited to propose candidates accompanied by brief bibliographic notes.
Nicolet also provided twelve copies of his UBV Catalogue for distribution, and the symposium prompted further technical work within the group, including the adaptation of the ALCEP program to microcomputer format. Overall, Marly 84 marked a moment of both scientific enrichment and organizational consolidation for GEOS.