The Neutral Night filter helps to improve image quality during astrophotography sessions in urban areas by reducing the appearance of light pollution from artificial light sources such as commercial or residential buildings, brightly lit billboards, streetlamps, and sports and entertainment venues that can produce a yellowish cast in your images.
These artificial light sources create a form of light pollution known as sky glow, where individual stars, the Milky Way, and other astronomical objects in the night sky are obscured. Employing this filter can improve the image quality by blocking the yellow light from sodium-vapor lamps, mercury-vapor lamps, or low Color Rendering Index LEDs. By preventing the dominant wavelengths of light associated with the color of those lamps from being recorded, the visibility of astronomical objects is enhanced. An additional IR-blocking lens coating is applied that prevents ghosting and blurriness from appearing on your images when using sensors that are sensitive to those low wavelengths.