Cleaning a first surface bare aluminum-coated optic: a method for comparing wash types

Patrick Dunlop; Ryan Ketterer; Matthew Evatt; Bob Stupak; Chris Stone

doi:10.1117/12.3018453

25 July 2024 Cleaning a first surface bare aluminum-coated optic: a method for comparing wash types

Patrick Dunlop, Ryan Ketterer, Matthew Evatt, Bob Stupak, Chris Stone

Author Affiliations +

Proceedings Volume 13098, Observatory Operations: Strategies, Processes, and Systems X; 130982L (2024) https://doi.org/10.1117/12.3018453
Event: SPIE Astronomical Telescopes + Instrumentation, 2024, Yokohama, Japan

Conference Poster

Abstract

Three different techniques for washing bare aluminum-coated telescope optics are studied by analyzing specular and diffuse reflectance data from two 4-meter class telescopes. The established “contact” wash method involves dabbing the mirror’s first surface with natural sponges and detergent, which subjects the coating to some level of abrasion. While this method proves effective at removing contaminants, it is more labor intensive, increases risk to the optics, and induces contact of the first surface. The industry established CO₂ “snow” wash to clean the optics at an increased regular interval. This method utilizes thermal properties and pressure to clean the first surface, and is well documented throughout the industry. An alternate “contactless” approach has been recently employed utilizing only pressurized water to mechanically agitate contaminants. This reduces the amount of labor and the risk to the optics, although the effectiveness of this method is yet to be determined. A comparison of these three wash methods is presented using long-term specular and diffuse reflectance data from two 4-meter class telescopes. Data taken from multiple telescopes offers the opportunity to gain generalized insights into each wash method’s performance. Despite challenges of comparing data from different mirrors, coatings, and environments, we attempt to establish trends of their relative results independent of the unique degradation profile of each mirror and coating.

(2024) Published by SPIE. Downloading of the abstract is permitted for personal use only.

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Patrick Dunlop, Ryan Ketterer, Matthew Evatt, Bob Stupak, and Chris Stone "Cleaning a first surface bare aluminum-coated optic: a method for comparing wash types", Proc. SPIE 13098, Observatory Operations: Strategies, Processes, and Systems X, 130982L (25 July 2024); https://doi.org/10.1117/12.3018453

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