$60 new from Orion - yours for $48 including shipping.
Advanced multilayer “interference” filter that blocks the most common wavelengths of light pollution while passing desirable wavelengths with very little attenuation, yielding dramatically better deep-sky views.
SkyGlow filters feature improved blocking of mercury-vapor light and higher transmission at critical hydrogen-alpha and hydrogen-beta lines than competing filters. Bright, light-polluted skies appear much darker, and the contrast between object and sky is improved significantly.
Enhances All Objects
This contrast-enhancement effect is particularly apparent on nebulas. Unlike stars, emission nebulas give off light in a very narrow range of wavelengths. SkyGlow filters allow maximum transmission of the important wavelengths of hydrogen-alpha, hydrogen-beta, and doubly ionized oxygen-the ones most commonly emitted by nebulas. Views of galaxies and star clusters are also enhanced, although not as much.