Grey filters can be used for planet observing, solar observing (only in combination with a true solar filter!) and for nature observing. The function is similar to regular sunglasses - the image brightness is reduced, meaning less strain for your eyes. The filter can be used visually and photographically..
An ND filter is also helpful for observing binary stars by reducing the glare of the brighter component.
The filters are simply screwed into the 1.25" filter thread of the eyepiece or camera adaptation. The filter is also available in 2" (see separate product description).
The smaller the percentage of light transmission, the stronger the filter is. For example a 25% filter will allow 1/4 of the light to pass through, while the rest will be blocked. A 12.5% filter will transmit only 1/8 of the light.
Scope of Delivery:
-- Grey (Neutral Density) Filter 1.25"
-- Protective box (plastic)