The "physics of astrophysical observations". Radiative processes, in general, including spectral line formation in static and moving media and radiative transfer. Fundamentals of hydrodynamics relevant to cosmic environments: self-similarity, viscous and vortical extensions of the equations of motion, fundmental fluid instabilities and dimensionless numbers, turbulence; application to particular astrophysical problems (e.g. interstellar medium, explosive phenomena, winds and outflows, accretion disks)