Optical design of Gemini Altair

Eric Harvey Richardson; J. Murray Fletcher; Christopher L. Morbey; Jacobus M. Oschmann; John Stanley Pazder

doi:10.1117/12.321718

11 September 1998 Optical design of Gemini Altair

Eric Harvey Richardson, J. Murray Fletcher, Christopher L. Morbey, Jacobus M. Oschmann, John Stanley Pazder

Proceedings Volume 3353, Adaptive Optical System Technologies; (1998) https://doi.org/10.1117/12.321718
Event: Astronomical Telescopes and Instrumentation, 1998, Kona, HI, United States

Abstract

The 8-meter Gemini telescope's adaptive optics (AO) module, Altair, is 'transparent' in that it does not change the focal ratio, being f/16 in and f/16 out; it has the same focal position as the bare telescope, with insignificant change in the exit pupil. However, Altair has a flat focal surface, unlike other AO designs which have focal surfaces curved more than the focal surface of the bare telescope and in the opposite direction. An unusual requirement for Altair is that the atmospheric layer 6.5 km above the telescope should be imaged onto the deformable mirror. Other requirements are minimization of distortion in the wavefront sensor module for both the imaging of the deformable mirror onto the lenslet array and for the reimaging of the approximately 230 lenslets' images onto a CCD, for a natural guide star, and also for a Sodium laser guide star ranging in object distance form 85 km to 156 km. The separation of natural and laser star beams is done with minimum light loss by passing the in-focus natural star image through a pinhole which is smaller than the shadow of the secondary mirror of the telescope in the out-of-focus laser beam which is reflected by the tilted pinhole mirror.

Citation Download Citation

Eric Harvey Richardson, J. Murray Fletcher, Christopher L. Morbey, Jacobus M. Oschmann, and John Stanley Pazder "Optical design of Gemini Altair", Proc. SPIE 3353, Adaptive Optical System Technologies, (11 September 1998); https://doi.org/10.1117/12.321718

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