Refractors are rarely used in industrial applications primarily due to cost and aperture size. However, many amateurs and semi-professional clients have approached us and asked us to design and develop refractors for purely astronomical use. These tend to be almost entirely apochromatic systems where the use of specialised glass types is essential to achieve the high standards required in what are usually fast, wide field instruments. We have both design and manufacturing capabilities to offer apertures up to and including 300mm in a variety of formats from single lenses to 4 element, complex designs. The key to designing efficient refractors is the choice of glass. Specialist glass is available in hundreds of different types and characteristics, some of which are common and relatively inexpensive, others are limited by the size of the manufactured, cast glass blank. Many glass types are only produced in slabs of up to 127mm so designing a large refractor has to obviously take these limitations into account. Some glass types are also attacked by the atmosphere around us, especially in humid environments. Finger marks can stain a polished glass surface if the choice is badly made on glass type. At Orion Optics we thoroughly investigate the usability of all the glasses used in our designs to ensure no problems can arise for clients in the environment where their instrument is being used. Below you will find a typical screenshot of an apochromatic refractor is design stages.