Parameter degeneracy in models of the quadruple lens system Q2237+0305

The geometry of the quadruple lens system Q2237+0305 is modeled with a simple astigmatic lens: a power-law mass distribution: m ~rbeta^ with an external shear γ. The image positions can be reproduced with an accuracy better than 0.01 arcsec for any 0.0 <= β <= 1.85 and the corresponding value of γ = 0.1385-0.0689β. This is a factor of ~4 more precise than what can be achieved by the best constant M/L lens models [Rix et al., AJ, 104,959(1992)]. The image intensity ratios and the time delay ratios are almost constant along our one parameter family of models, but the total magnification varies from 8 to > 1000, and the maximum time delay (between leading image B and trailing image C) for H_0_ of 75 km s^-1^ Mpc^-1^ varies from more than 20 h to about 1.5 h, while β increases from 0.0 to 1.85.