This book addresses graduate students in astronomy andastrophysics. The first part is devoted to galactichigh-energy astrophysics. It treats particle accelerations(including shocks), the interstellar medium and supernovaeremnants, high-energy emissions from normal stars andaccretion in close binaries. The second part deals withobservationslike pulsar timing, and its measurement withradioastronomical tools, and astrometry, as performed in theHIPPARCOS satellite program.