Fast camera objective designs for spectrograph of Mont Megantique telescope

All-reflective optics is conventionally required for extended spectral region observations in astronomical spectrograph. But the spatial resolution is usually not good enough while the large-size CCD will be used for observation in all-reflective optics. In this paper, all-refractive optics has been investigated to design a fast (F/1.55) and wide angle camera objective for large spectral coverage, from UV to VIS and up to NIR, when a large-size CCD is used on the focal plane of the spectrograph of Mont Megantique telescope. The case of achromatic and apochromatic condition has been investigated for axial and lateral color controls. The new proposed solutions have been optimized from two to three different glass combinations in order to have higher throughputs for large spectral coverage, especially in UV region. The used components have been minimized to reduce the light inherent lost. The monochromatic aberrations have been corrected and controlled by using optimized lens bending and shapes to make the camera have the CCD pixel resolution. Ray tracing results displayed the good optical performance of the camera to cover from 350 nm to 1000 nm spectral region with high resolution. The broadband AR coating, enhanced on UV region, will be used on each surface of the lenses in the camera. Final throughputs for the designed camera has been estimated and given in the paper.