OLED is an observational project proposed by the Federación de Asociaciones Astronomicas de España and the Société Astronomique de France, aimed at amateur observers interested in measuring lunar occultations of double stars and using photometric techniques applied to these events. These techniques allow to obtain the light curve of a double star occultation, and from it, the measurement of its parameters, separation and position angle, with data obtained from two or more observers. Data from single observers are also valuable. It is therefore a collaborative project, like other projects such as asteroidal occultations. In the case of lunar occultations the events are not local phenomena, but their visibility is spread across a large geographical area, which makes things easier since it is not necessary to travel to specific locations: lunar occultations can be observed from our usual observing site. This aspect renders lunar occultation work ideal for international collaboration.

The objective is to study close double stars (which are more difficult to measure with other techniques), especially those with only one measurement or with few historical measurements.