This collection includes optical monitorings of gravitationally lensed
quasars. The frames can be used to make light curves of quasar images
and field objects. From quasar light curves, one may measure time
delays and flux ratios, analyse variability and chromaticity, etc.
These direct analyses/measurements are basic tools for different
astrophysical studies, e.g., expansion rate of the Universe, mechanism
of intrinsic variability in quasars, accretion disk structure,
supermassive black holes, dark halos of galaxies (dust, collapsed dark
matter, smoothly distributed dark matter,...)
