Telescope uses specialist lenses in optical corrector

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The International Liquid Mirror Telescope (ILMT) is using lenses from Optical Surfaces as part of its Time Delay Integration (TDI) optical corrector unit.

Due to be installed at Devasthal (India) the International Liquid Mirror Telescope is made up of three main components: a primary rotating mirror, a focal structure and a CCD camera with optical corrector. The ILMT uses Liquid Mirror technology whereby the primary mirror of the telescope is a rotating container with a highly-reflecting liquid (mercury) in it. The surface of the spinning liquid takes the shape of a paraboloid. As the primary mirror of the ILMT is parabolic, the off-axis imaging is distorted by spherical, coma and time delay integration (TDI) aberrations. In order to correct these off-axis aberrations and to increase as much as possible the field of view of the telescope, an optical corrector must be inserted before the CCD camera.

Stefan Denis, project manager at AMOS, a supplier to ILMT, commented: 'The lenses manufactured by Optical Surfaces are to be assembled into our TDI optical corrector, which - beside the basic field correction - aims at correcting for the trajectory of stars passing by at the zenith of the ILMT.' The supplied high precision lenses were of various sizes - the largest of which was a 465mm diameter steep meniscus. He added: 'Optical Surfaces was selected for its well-known high-level quality in optical manufacturing, including off-axis and special shape optics'.