This book addresses graduate students in astronomy and astrophysics. The first part is devoted to galactic high-energy astrophysics. It treats particle accelerations (including shocks), the interstellar medium and supernovae remnants, high-energy emissions from normal stars and accretion in close binaries. The second part deals with observationslike pulsar timing, and its measurement with radioastronomical tools, and astrometry, as performed in the HIPPARCOS satellite program.