The first set of optics for a MOONS camera have been delivered and successfully mounted into their housings. The six near-identical cameras in the MOONS spectrograph all use the same innovative optical design, more information on which can be found here. This first set of optics is for one of the two YJ-band cameras. Five more sets of optics will follow.

The lens assembly in its housing. Note the square L2 lens which is bonded into a hole in the large L1 lens.

The cameras were designed in Florence and have been manufactured by Winlight in France; while the mechanical housings have been developed at the University of Cambridge. Each optic is approximately 44 cm in diameter, which makes handling especially difficult. In the pictures the complex support structure to hold the lens can be seen: the small radial ‘spokes’ contain spring-loaded pads that push on the lens to ensure that even as the cameras are cooled down to 130 Kelvin for operation, no additional stresses are placed on the components and also the lenses stay centred and aligned.

The mirror in its housing. The radial ‘spokes’ are the supports that keep the optic aligned.

The beauty of the MOONS camera design is that although there are three optical elements to bring the light to a focus on the detector, because the L1 and L2 are glued together, you only have to adjust the position of the mirror to bring the system to a focus – contrast this with the number of degrees of freedom that are possible if the three optical elements are free to move independently. Cambridge will now begin the exciting task of aligning this first camera.

The optical design of the MOONS camera, clearly showing the hole in L1 where L2 (and the detector) sit.
The fully assembled camera system.




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