Founded in 1974, GEOS has been guided by a passion for variable‑star research and the power of collaboration, while upholding excellence in observation, careful data reduction, and community‑driven science.
Building on these values, GEOS pursues its mission through the following core objectives:
Since its founding, GEOS brings together amateur and professional astronomers across Europe (France, Spain, Italy, Germany, Belgium, Switzerland, etc.).
His Purpose is enabling amateurs with modest equipment to contribute to astrophysical research.
He encourages amateurs to extract scientific information from their own observations and publish results.
The main activity is the observation of variable stars (RR Lyrae, Cepheids, δ Scuti, eclipsing binaries, cataclysmic stars …).
Early methods were visual estimations using comparison stars (Argelander method), later modern methods as CCD photometry allowed to improve precision and reliability of amateur observations.
GEOS members publish results in journals, conference proceedings, and circulars.
GEOS organizes an annual meeting and since 2020 monthly videoconferences
Since its creation, GEOS has produced more than 1550 circulars and maintains a bibliography allowing their download.
Among them are the GEOS CIRCULARS, classified by star type and peer-reviewed. The most important ones are deposited on arXiv/astro-ph when possible.
Several publications in specialized journals, which he initiated or contributed to, are among GEOS main successes.
GEOS encourages amateurs, even with small telescopes or binoculars, to participate and provides training in photometry, data reduction, and analysis with the purpose of making astrophysics accessible and inspire new generations of observers.
