● Infrared light is invisible to the human eye, so general astronomical telescopes are not designed to focus on infrared light. While there is no problem when using a telescope for visual observation, most CMOS camera sensors are highly sensitive to infrared light, and images in the visible light range will be degraded if captured without any filters. (The image will appear blurry.) Therefore, by using an IR cut filter, you can block infrared light from reaching the CMOS camera sensor, resulting in a clearer image. ● Also, when photographing the solar surface in the Hα region, it protects the delicate and expensive Hα filter from the effects of infrared light. ※ Many commercially available light pollution reduction filters and narrowband filters cut the infrared region, so an IR cut filter is not necessary if you are using these filters. (There is no need to use them together.) Main Specifications Filter Size: 1.25" Thickness: Filter frame height: 5mm + Thread height: 2.5mm Mounting Standard: M28.6