We present VR observations of QSO 2237+0305 conducted by the GLITP
collaboration from 1999 October 1 to 2000 February 3. The observations were
made with the 2.56 m Nordic Optical Telescope at Roque de los Muchachos
Observatory, La Palma (Spain). The PSF fitting method and an adapted version of
the ISIS subtraction method have been used to derive the VR light curves of the
four components (A-D) of the quasar. The mean errors range in the intervals
0.01-0.04 mag (PSF fitting) and 0.01-0.02 mag (ISIS subtraction), with the
faintest component (D) having the largest uncertainties. We address the
relatively good agreement between the A-D light curves derived using different
filters, photometric techniques, and telescopes. The new VR light curves of
component A extend the time coverage of a high magnification microlensing peak,
which was discovered by the OGLE team.Comment: 15 pages, 3 figures, ApJ accepted (Feb 19
