Neutral density polarising filters are the best solution to manually adjust the brightness of the observed object maintaining its original colour.
This filter is an assembly of two separate glasses that can be rotated to adjust the light transmission between 1% and 40%. This is particularly useful to reduce the glare and the brightness of the Moon, especially at low magnification when the Moon appears too bright.
The filters are glass filters and the cell is made of anodised aluminium for high durability.
This filter can be screwed onto any standard 2' eyepiece (M48 x 0.75).
Do not use this filter for solar observations.