Daystar ERF 140mm with 200mm Cap - E-200N140

140mm ERF Glass, Cell & 200mm ID Cap - For Refractors Discontinued DayStar Energy Rejection Filters reduce the heat load on your filter assembly by absorbing or reflecting UV and/or I light and transmitting light in the desired visual spectrum. These filters are sometimes Red or Yellow glass, or dielectric IR and UV, but pass light in the desired visual spectrum. The ERF can also serve as an aperture mask to accomplish a straight angle of incidence for light entering the filter. DayStar filter assemblies operate best at f/30 and slower. Creating f/30 configuration can be done easily with the proper ERF and/or barlow. Higher resolution, larger aperture configurations use a barlow. ***This is a research-grade product that is made-to-order in the United States. Currently, this product has a 4-6 week delivery wait. Please contact us to confirm lead time. In the order notes, please specify the telescope this ERF is to be used with, and measure (with a ruler) the outside (largest) diamet