The filter is a multi-band pass filter which transmits a high percentage of light in the visual spectrum. It will enhance contrast when observing brighter objects such as the moon and planets and in the same time will suppress sky glow from artificial lighting and background reflected glow. The filter has a mild effect of darkening the background of the night sky so that the fainter objects will be against the dark background, excellent for observing planets. The filter will fit all standard sized 2" eyepieces and accessories such as Barlow lens etc. It is mounted in a nicely anodized Al alloy housing and is threaded on both sides for stacking with other 2" filters if necessary.