The dark energy camera's optical corrector

This thesis details the design, construction and alignment of the Dark Energy Survey's optical corrector. The Dark Energy Camera (DECam) is a new wide-�field corrector with a 2.2 square degree fi�eld of view and �five �filters covering the visible wavelengths. It has been commissioned as an upgrade for the Blanco telescope at the Cerro Tololo Inter-American Observatory in Chile. The initial discussion in this thesis centres on the verification of the compression modulus of the rubber used in the opto-mechanical design. Experimental results are compared against the theoretical models used in the design of the optical corrector. This leads into the techniques created to ensure the identical reproduction of these rubber pads. The testing of the chemical composition of the cell material is then explored along with its thermal expansion properties in order to determine compliance with the specifi�cations. The discussion on the design of DECam is completed with the metrology of the cells and the mapping of the variations from at and the non-circularity on the alignment surfaces. The thesis then extends to the alignment of the lenses (both prototype and DECam) within their cells and the tolerances to which they are held. Finally the e�ffect of misalignment of the lenses on the weak lensing signal was investigated. Each lens was considered individually and then random misalignments were used to look at multiple lens misalignments. A quantitative system was used to determine the relative importance of the lenses for ensuring the best possible optical performance from the perspective of the weak lensing community