Coating the 8-m Gemini telescopes with protected silver

Maxime Boccas, Tomislav Vucina, Claudio Araya, Esteban Vera, Clayton Ahhee

Research output: Contribution to journalConference articlepeer-review

59 Scopus citations


The Gemini telescopes were designed to be infrared-optimized. Among the features specified for optimal performance is the use of silver-based coatings on the mirrors. The feasibility study contracted by Gemini in 1994-1995 provided both techniques and recipes to apply these high-reflectivity and low-emissivity films. All this effort is now being implemented in our coating plants. At the time of the study, sputtering experiments showed that a reflectivity of 99.1% at 10μm was achievable. We have now produced bare and protected silver sputtered films in our coating plants and conducted environmental testing, both accelerated and in real-life conditions, to assess the durability. We have also already applied, for the first time ever, protected-silver coatings on the main optical elements (M1, M2 and M3) of an 8-m telescope. We report here the progress to date, the performance of the films, and our long-term plans for mirror coatings and maintenance.

Original languageEnglish
Pages (from-to)239-253
Number of pages15
JournalProceedings of SPIE - The International Society for Optical Engineering
StatePublished - 2004
Externally publishedYes
EventOptical Fabrication, Metrology, and Materials Advancements for Telescopes - Glasgow, United Kingdom
Duration: 24 Jun 200425 Jun 2004


  • Durability
  • High-reflectivity
  • Low-emissivity
  • Silver coating
  • Sputtering


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