The sixth annual GEOS symposium was held in Marly‑le‑Roi on 24–26 April 1981, bringing together about forty observers from Belgium, Spain, France, and Italy. The meeting focused on observational results, period analyses, methodological issues, and the organisation of future work. C. Romoli presented new results on RZ Cep, confirming that its O–C curve shows a periodic but non‑sinusoidal behaviour. Using photoelectric maxima, he derived a Blazhko period of about 96 days and noted a small bump occurring shortly before maximum light.
Figer reviewed the case of NN Cep. He showed that the results originally published by R. Rolland in 1977—period, EB classification, and identification of primary and secondary minima—have since been fully confirmed by independent photographic and photoelectric studies. This was highlighted as an important success for GEOS visual observers.
A broad review of stars from the Catalogue of Suspected Variables was presented, summarising preliminary findings for several dozen objects. Some appear clearly variable, others constant, and many show contradictory or insufficient data requiring further observation.
Gaspani reported on orbital analyses of several eclipsing binaries (KR Lac, MQ Cep, GS Lac, LW Lac) based on Vatican and Hamburg photographic archives. He also analysed the long‑term O–C behaviour of W UMa, interpreting early variations as the effect of a third body.
Updates on CY Aqr and DY Peg underlined the difficulty of detecting weak Blazhko effects. Figer noted that periodograms must be used with caution when dealing with very small modulations.
Buzzoni presented a critical study of visual photometry, arguing that the classical linear relation between magnitude differences and visual “steps” is inadequate. He proposed a non‑linear model that better explains known biases such as the Carnevali effect.
Several observing campaigns were proposed, including a programme on Be stars —considered a promising field for GEOS— and a collaboration with professional astronomer A. Bianchini on old novae.
Michel Petit presented a detailed review of FG Sge, describing its rapid and exceptional evolution over recent decades, which provides rare observational insight into the final stages of stellar evolution.
The symposium concluded with discussions on group organisation, support for beginners, external visibility, and the adoption of a new five‑category structure for the GEOS observing programme.