The present site is maintained by Jean-Francois Le Borgne (leborgne [at] ast.obs-mip.fr)

GEOS (Groupe Européen d’Observation Stellaire) is a more than thirty-years-old group of amateur and professional astronomers. It is composed by variable star observers belonging to a number of European countries. The group’s main purpose is to observe variable stars and process the data thus collected with research work as a final objective. [see site]
The present web site is mainly dedicated to the variable stars of RR Lyr type.

GEOS RR Lyr database

The GEOS RR Lyr database is intended to help observations and studies on RR Lyr stars. It contains times of light maximum of RR Lyr stars obtained either visually or with electronic devices or photographically. The stars concerned are field RRab and RRc. The observations are collected in the litterature or submitted by observers. It presently contents some 42000 maxima on more than 2000 stars. The former version of the database web site is still available at http://dbrr.ast.obs-mip.fr

GEOS RR Lyr Survey

The GEOS RR Lyr Survey participates to maintain the follow up of the variation of period and Blazhko effect of RR Lyr stars. These period variations are known to have time scales of days to centuries. Their study then requires an effort to collect observations over years. To achieve this aim, the GEOS RR Lyr Survey project performs 2 kinds of observations:

• The recording of maximums of bright (magnitude at minimum less than ~12.5) well studied RR Lyr stars. For this we use the automatic telescopes TAROT [see site]. One is located at Calern Observatory in Europe and one at La Silla Observatory in Chile.
• The detailed study of under-studied RR Lyr stars in the magnitude range 12 to 15. This part of the project is provided by the observations of amateur astronomers using 20 to 60 cm diameter telescopes and CCD cameras.

The bibliography associated to the building of the RR Lyr database is available at http://dbrr.ast.obs-mip.fr/rrlyrbib.html

Astronomical ephemeris

This link gives access to a small php code allowing to compute astronomical ephemeris. In particular, it is possible to compute the geocentric correction necessary for RR Lyr stars observations, but also julian dates, sidereal time ...

People Project coordinator (RR Lyr Survey and database): Jean-Francois Le Borgne (Toulouse, France) [see private site] Database maintenance: Jean-Francois Le Borgne (webmaster), Anton Paschke, Massimiliano Martignoni, Francesco Acerbi, Jacqueline Vandenbroere (data collection). Tarot Telescopes: Jean-Francois Le Borgne (RR Lyr program), Alain Klotz (telescope manager), Michel Boer (TAROT PI). CCD and visual observations:  Neil Butterworth (Townsville, Australia, CCD, Meade LX200)  Laurent Corp (Rodez, France, CCD, T200) [see private site]  Eric Denoux (Caussade, France, CCD, C14) [see private site]  Shawn Dvorak (Rolling Hills, Florida, USA, CCD, C11) [see private site]  Francesco Fumagalli (Bergamo, Italy, CCD, T300)  F.-J. (Josch) Hambsch (Belgium, CCD, T280, T350 and T500) [see private site]  Friedhelm Hund (Hakos Farm, Namibia, CCD, C11)  Dieter Husar (Belgium + Germany, CCD, T200 + T400) [see private site]  Jean marie Llapasset (Perpignan, France, CCD, C11) [see private site]  Gisela Maintz (Bonn, Germany, CCD, T200) [see private site]  Joel Nicolas (Vallauris, France, CCD, C11)  Charles Olivi (Cannes, France, CCD, C11)  Anton Paschke (Zurich, Switzerland, CCD, T300) [see private site]  Philippe Roblin (La Rochelle, France, CCD, T300) [see private site]  Jacqueline Vandenbroere (Heure, Belgium, visual, T200) Theory gurus: Ennio Poretti (Milano, Italy), Juan Fabregat (Valencia, Spain)