0.965 Inch Nebula Contrast Filter

This 0.965 inch (24.5 mm) nebula filter is built for practical deep-sky observing from UK backyards and suburban locations. Its core function is contrast enhancement: the red interference coating reduces skyglow while preserving nebular signal, resulting in visibly darker backgrounds and stronger definition of extended nebulosities. The filter uses optical glass mounted in a precisely machined aluminum alloy frame — robust enough for frequent insertion/removal yet light enough (6 g) to avoid strain on focuser mechanisms. It threads directly onto any standard 0.965 inch eyepiece barrel or adapter, requiring no tools or modification. Field reports confirm improved detection of faint extensions in objects like the Veil Nebula and greater visibility of filamentary structure in the Orion Nebula M42. It also functions effectively on the Moon — suppressing halation around bright craters and increasing perceived sharpness of fine terrain features without dimming the overall view excessively.