Optical monitoring of the gravitationally lensed quasar Q2237+0305 from   APO between June 1995 and January 1998
  We present a data set of images of the gravitationally lensed quasar Q2237+0305, that was obtained at the Apache Point Observatory (APO) between June 1995 and January 1998. Although the images were taken under variable, often poor seeing conditions and with coarse pixel sampling, photometry is possible for the two brighter quasar images A and B with the help of exact quasar image positions from HST observations. We obtain a light curve with 73 data points for each of the images A and B. There is evidence for a long (>~ 100 day) brightness peak in image A in 1996 with an amplitude of about 0.4 to 0.5 mag (relative to 1995), which indicates that microlensing has been taking place in the lensing galaxy. Image B does not vary much over the course of the observation period. The long, smooth variation of the light curve is similar to the results from the OGLE monitoring of the system (Wozniak et al. 2000a). 
R. W. Schmidt (1,2), T. Kundic (3), U.-L. Pen (4), E. L. Turner (5),   J. Wambsganss (2), L. E. Bergeron (6), W. N. Colley (...