The ionised gas regions, which are the main tracers of the spiral arms, can be used for the study and determination of the spiral structure of our Galaxy. Towards this goal, the Marseille Observatory elaborated and developed an instrument, using a scanning Fabry–Perot interferometer, particularly suited for the observation of extended objects. A survey of the southern Galactic plane then started at the beginning of 1990. The major instrumental aim is to obtain spectral information, and therefore the ionised gas kinematics, in each pixel of the observed fields. Already 300 fields of 38′×38′ have been observed in Hα with a spatial resolution of 9″×9″, covering almost the entire fourth quadrant of the Galactic plane, and numerous discrete HII regions have been detected, as well as diffuse emission which is widely distributed. Also, the Magellanic Clouds have been studied using the same instrument.

The Magellanic Clouds possess extensive systems of rich star clusters. These objects span a wide range in age and metal abundance, and are close enough to be fully resolved into individual stars. They represent the most accessible examples of such clusters and are therefore key to a wide variety of astronomical research. In this contribution I describe recent results from work on several problems in Magellanic Cloud cluster astronomy of relevance to The Ages of Stars. These include testing and constraining stellar evolution and simple stellar population models, investigating the formation and evolution of the Clouds themselves, and the discovery of several intermediate-age clusters which apparently possess more than one stellar population.