WEAVE spectrograph cameras: the polishing of the spherical lenses

Abstract

WEAVE is the new wide field multi-object and integral field survey facility for the prime focus of the 4.2 m William Herschel Telescope. WEAVE fiber-fed spectrograph offers two resolutions, R 5000 and 20,000. The dual-beam spectrograph has two cameras: the blue one optimized for the wavelength interval of 366 - 606 nm and the red one for 579 - 959 nm. Each camera is formed by eight lenses, one aspherical and seven spherical. The lenses of the red camera are identical to the lenses of the blue camera only differentiated by the anti-reflection coating wavelength range. The diameter of the largest surface is 320 mm while of the smallest is 195 mm. INAOE, as a member of the collaboration is responsible of the manufacturing of the 14 spherical lenses and the collimator mirror. Here, we describe the main characteristics of WEAVE high precision cameras lenses, the manufacturing challenges giving the combination of OHARA glasses properties, dimensions and specifications. We discuss the solutions developed to achieve the very demanding specifications.