The finite element analyses of two large lenses for the Keck Telescope High Resolution Echelle Spectrograph are described. The two lenses, one simple lens, and one meniscus, are of fused silica and are approximately 800 mm (30 in.) in diameter. The purpose of the analyses is to determine the deformations of each optic under its own weight, and to identify the simplest, most cost effective mounting cell that will satisfy the optical requirements. Two common radial supports are analyzed, including varieties of hard point and band type mountings. Several types of axial supports are examined including simple three-point mounts, ring mounts, and static deformation mounts. A parametric finite element input routine is described, whereby a solid model and finite element mesh are automatically generated, given the lens diameter, central thickness, and surface radii of curvature. Deformation predictions from the models are compared with theoretical calculations, interferometric testing, and precision profilometry.