Dark-Sky Filter 77mm Slim nefa this focal extender adds some

this focal extender adds some real versatility to your telescope accessory line-up

The brightness is enhanced by the large 42mm and 50mm apertures

and rich star fields with ease

More contrast and details for all urban observers and astrophotographers

Dark-Sky Filter 77mm Slim nefa this focal extender adds someUniversally applicable dark sky filter with 77mm filter thread for photo lenses. Particularly suitable for increasing contrast in aurora and deep sky photography. The wavelengths of 550nm (green) and 630nm (red), which are particularly relevant for aurora photography, are transmitted to more than 90%. A special feature of other so called CLS filters is that only the yellow light of the sodium line is effectively blocked at 590nmwill. This effectively