The OCS A45 was designed due to demand! FAST DOBS  have very steeply converging light cones coming off the secondary mirror. Since the OCS Optic must go deeply into the converging light cone to allow the Binotron 27 to reach focus, we made an optic that simply cannot be any larger in clear aperture and still be held securly in an anodized aluminum cell. The picture showing how large this optic is speaks for itself. Used with the Binotron-27 Super System, this optic grabs those outer peripheral rays missed by the OCS A37 and produces a brighter image. Alone this optic costs $249.00. Add it to a new Binotron 27 order and recieve a $100.00 discount! Please see "OCS A45 For New Binotron" under "products" and order it there IF you are also ordering any Binotron 27. A new Binotron 27 order must be placed to recieve the $149.00 price. This product listing included the OCS A45 Optic in Cell with machine cap only. It is shown on the Power Switch and Middle Newtonian Spacer for reference only and they are not included with the OCS A45 Optical Cell.