A new city light pollution filter! Triad Quadband Ultra Filter. - VisibleDark
Using OPT's TRIAD Ultra Quad-Band Filter Under Extreme Light Pollution
OPT Triad Ultra Quad-Band Schmalbandfilter 2"
OPT Telescopes - Have you heard about the Radian Triad Ultra Filter? This Filter allows you to cut straight through light pollution in even the most heavily light-polluted cities. This image was