It is an eyepiece filter for reducing the brightness of the moon and planets and improving contrast.
The filter has a mild effect of darkening the background of the night sky so that the fainter objects are more clearly seen contrasted against the blackness of space.
1.25" standard size for Celestron, Orion, Sky-watcher, Meade, William and any brands models.
All Study Aluminum Construction and Optical glass filter lens. Standard filter threads on both sides. So you can mount other filters together when using this filter,
The filter effectively filters out selective wavelengths of low-pressure sodium and other man-made sources typically used in street lighting. Although it is not a nebula filter, it enhances the views of deep-sky objects by increasing the contrast of these objects against the background sky.
