This 2" filter is threaded for 48 mm metric threads. It has a transmission rate of 1.8%, making it an ideal moon filter for large aperture instruments. Use this filter with the AstroSolar Density 3.8 Film for safe solar observation.
IMPORTANT! Do not attempt to use this filter without a white-light filter in front of your main telescope optics. While it will supplement the ND 3.8 Photographic Density filter material to yield a safe combined transmission level, it is wholly insufficient by itself for solar viewing. Serious damage to your eyes could result from improper use of solar filters!