SII Filters

The Ultra-Narrowband series comprises line filters with a very narrow full width at half maximum, recommended for optical systems with an aperture ratio of f/10 to f/3.5.

Due to the low full width at half maximum, the filters allow maximum contrast even in severe light pollution conditions. They minimise the size of stars and thus make the finest details accessible – indispensable under Bortle class 9/8/7/(6) skies.