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Prime Focus Corrector

At Prime Focus a four-element field corrector and a two-element atmospheric dispersion compensator are provided, the layout of these elements is shown in Figure gif. The field corrector provides good images over an unvignetted field 40 arcmin in diameter, and 45% vignetting at 1 degree diameter. The atmospheric dispersion corrector is specified to compensate for atmospheric dispersion over a wavelength range of 3300 to 11000Å, at zenith distances up to 73.

Tue Aug 15 16:42:46 BST 1995