Optical photometry is presented for the quadruple gravitational lens PG1115+080 .
A preliminary reduction of data taken from November 1995 to June 1996 gives component “ C ” leading component “ B ” by 23.7 \pm 3.4 days and components “ A1 ” and “ A2 ” by 9.4 days .
A range of models has been fit to the image positions , none of which gives an adequate fit .
The best fitting and most physically plausible of these , taking the lensing galaxy and the associated group of galaxies to be singular isothermal spheres , gives a Hubble constant of 42 km/s/Mpc for \Omega = 1 , with an observational uncertainty of 14 % , as computed from the B - C time delay measurement .
Taking the lensing galaxy to have an approximately E5 isothermal mass distribution yields H _ { 0 } = 64 km/sec/Mpc while taking the galaxy to be a point mass gives H _ { 0 } = 84 km/sec/Mpc .
The former gives a particularly bad fit to the position of the lensing galaxy , while the latter is inconsistent with measurements of nearby galaxy rotation curves .
Constraints on these and other possible models are expected to improve with planned HST observations .