The brochure “Filters for Astronomy & Aerospace” from Omega Optical Inc. details the company’s Bessell photometric sets, which are polished to transmitted wavefront, wedge and flatness specifications, and its custom filters, which are available in quantities of 10 to 1000 in the UV to mid-IR range. Downloadable from the company Web site, the document notes that many of the filters are available as sets with matching physical attributes. Large-format filters in sizes up to 210 mm in diameter are described, along with narrowband filters, interference passband filters and photometric filter sets that isolate broad areas of the spectrum.