We present the design, assembly, alignment, and verification process of the wide field corrector for the Korea Microlensing Telescope Network (KMTNet) 1.6 meter optical telescope. The optical configuration of the KMTNet telescope is prime focus, having a wide field corrector and the CCD camera on the topside of Optical Tube Assembly (OTA). The corrector is made of four lenses designed to have all spherical surfaces, being the largest one of 552 mm physical diameter. Combining with a purely parabolic primary mirror, this optical design makes easier to fabricate, to align, and to test the wide field optics. The centering process of the optics in the lens cell was performed on a precision rotary table using an indicator. After the centering, we mounted three large and heavy lenses on each cell by injecting the continuous Room Temperature Vulcanizing (RTV) silicon rubber bonding via a syringe.
L2 Tech, Inc. is in development of an innovative infrared-transparent glass ceramic material with low-thermal expansion
(<0.5 ppm/°C) and high thermal-shock resistance to be used as windows and domes for high speed flight. The material is
an inorganic, non-porous glass ceramic, characterized by crystalline phases of evenly distributed nano-crystals in a
residual glass phase. The major crystalline phase is zirconium tungstate (ZrW2O8) which has Negative Thermal
Expansion (NTE). The glass phase is the infrared-transparent germanate glass which has positive thermal expansion
(PTE). Then glass ceramic material has a balanced thermal expansion of near zero. The crystal structure is cubic and the
thermal expansion of the glass ceramic is isotropic or equal in all directions.
The fabrication and testing of a corrector mirror for a reflective Schmidt camera is to be presented. With a reflective corrector, the incident beam has to be off-axis. The corrector is tilted at an angle of 30 degrees with the optical axis to implement this requirement. The figure of the corrector, which composes of the toric term, rotational symmetrical and rotational nonsymmetrical aspherical terms, poses a certain degree of challenge for fabrication. The total correction is 46 waves peak to valley at 632.8 nm wavelength.