19 July 2010 Saving SALT: repairs to the spherical aberration corrector of the Southern African Large Telescope (SALT)
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Abstract
The construction of the Southern African Large Telescope (SALT) was largely completed by the end of 2005. At the beginning of 2006, it was realized that the telescope's image quality suffered from optical aberrations, chiefly a focus gradient across the focal plane, but also accompanied by astigmatism and higher order aberrations. In the previous conference in this series, a paper was presented describing the optical system engineering investigation which had been conducted to diagnose the problem. This investigation exonerated the primary mirror as the cause, as well as the science instruments, and was isolated to the interface between the telescope and a major optical sub-system, the spherical aberration corrector (SAC). This is a complex sub-system of four aspheric mirrors which corrects the spherical aberration of the 11-m primary mirror. In the last two years, a solution to this problem was developed which involved removing the SAC from the telescope, installing a modification of the SAC/telescope interface, re-aligning and testing the four SAC mirrors and re-installation on the telescope. This paper describes the plan, discusses the details and shows progress to date and the current status.
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Darragh E. O'Donoghue, James O'Connor, Lisa A. Crause, Francois Strumpfer, Ockert J. Strydom, Janus D. Brink, Craig Sass, Eben Wiid, Eli Atad-Ettedgui, "Saving SALT: repairs to the spherical aberration corrector of the Southern African Large Telescope (SALT)", Proc. SPIE 7739, Modern Technologies in Space- and Ground-based Telescopes and Instrumentation, 77390Q (19 July 2010); doi: 10.1117/12.856239; https://doi.org/10.1117/12.856239
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KEYWORDS
Telescopes

Computer generated holography

Mirrors

Monochromatic aberrations

Interfaces

Image quality

Optical alignment

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