The American company Chroma Technology Corp., based in Vermont, produces high-quality, custom-fit astronomy filters, which are manufactured with hard coatings of individual substrates made of best quality glass, with no need for lamination. All primary filter coatings on the front side, as well as additional anti-reflection coatings on the back of the filters, prevent ghosting and guarantee maximum transmission. These filters’ bandpass remains stable in their spectral range and are unchanged even when exposed to extreme temperature fluctuations or changes in humidity. All filters can also be used with fast apertures of f/4 or smaller. Chroma also offers customised coatings for more demanding applications, optimised for even faster apertures such as f/3 or f/2. On request, other filter sizes and unique passbands can also be made to order.