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Bugger, I just found this.
1. Refractor. Most refractor telescopes have multiple objective lens systems that are permanently mounted in cells or are permanently attached to the optical tube assembly (OTA). Because of their closed optical tube design, only the exposed surface of these optics will ever need to be cleaned. Again, most refractors do not have user "collimatable" optics and must be returned to the factory for optical alignment. Never disassemble a lens cell, under any circumstance, while many are air-spaced, others are vacuum sealed or filled with an inert gas such as nitrogen or even oil!
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