Optical cleanliness has long been a source of concern for astronomers. This concern is legitimate since dust is so ubiquitous, keeping it completely off the telescope's optics is nearly impossible. However, by using this dust cover when you're in between observing runs, you don't have to allow dust to reach your optics. Proudly made in the USA, the AstroZap Dust Cover is made from a fabric consisting of a blend of cotton and nylon. An elastic strap enables a solid fit over the open end of truss-tube RC dobsonians. This protects the primary and secondary mirrors from gathering dust, resulting in sharper images.