The Lumicon 1.2" Neutral Density 13 (ND13) Filter transmits 13% of all incident light, while blocking 87%.
The 1.25" filters employ industry-standard 1.125" x 42 tpi threads (except for Questar/Brandon, which use a thread pattern unique to Questar). The 48 mm filters employ industry-standard 48 x 0.75 mm threading, which thread into 2" eyepieces. All larger filters use the given size with 0.75 mm pitch (e.g. a 72 mm Minus Violet filter has 72 x 0.75 mm threads).
Recommended for lunar observing with 8" (200mm) and larger telescopes
Lumicon Neutral Density Filters are made from renowned Schott and Hoya optical glass and allow for maximum contrast on viewing planetary and lunar detail
Individually precision ground, highly polished with maximum light transmission coatings on both sides, these filters are 100% guaranteed for life
Neutral Density filters have four main uses
To enable slow shutter speeds to be used, especially with high speed films, to record movement in subjects such as waterfalls, clouds, or cars
To decrease depth of field by allowing wider apertures to be used, which helps separate subjects from their background
To decrease the effective ISO of high speed film (above ISO 400) and allow it to be used outdoors in bright situations
To allow cine and video cameras (which have fixed shutter speeds) to film subjects such as snow, sand or other bright scenes which could cause overexposure