Schw - shoc
- Schwarzschild metric
- Schwarzschild radius
- scintillation
- scintillation counters
- SE stars
- seasonal phenomena
- seasons
- secondary cosmic rays
- secondary mirrors
- secular parallax
- seeing
- seeing monitors
- segmented optics
- seismology
- selection effects
- selective absorption
- selenology
- self absorption
- self calibration methods
