Double stars
The aim of the OLED project is to study double star astrometry using lunar occultations. This is a very accurate technique, comparable in spatial resolution to some interferometric techniques, and therefore ideal to access binary stars with angular separations in the range 0.010"-0.1". We expect to be able to measure double stars that are not accessible to standard visual or speckle interferometric techniques available to the amateur. Also, the collaboration between groups of observers allow for the determination of two-dimensional positions, rather than the standard one-dimensional (projected) solutions normally obtained from single observations.
Lunar occultations of stars have historically played an important role as a method for measuring a uniform time scale (the so-called Ephemeris Time), impossible to materialize using traditional methods based on the (irregular) rotation of the Earth. Nowadays, the development of atomic clocks, based on quantum transitions of certain atoms, allows for the construction of a highly uniform scale independent of the Earth's rotation. This is one of the reasons why lunar occultations have lost interest within the professional astronomical community.
However, over the years, lunar occultations have undergone other vicissitudes unrelated to the measurement of a uniform time, some positive, some negative. These phenomena greatly contributed to the knowledge of the lunar limb, and consequently the topography, of the lunar surface. Additionally, they helped to assess the accuracy of lunar ephemerides and stellar ephemerides (i.e., the precision of star catalogues regarding position and proper motions).
Nevertheless, recent advances in celestial mechanics, the improvement of stellar astrometry (for example, Gaia), and lunar topographic surveys carried out by various probes orbiting the Moon, have once again relegated lunar occultations to a corner of history: few professional or amateur astronomers are involved in lunar occultations.