The Optical Vision 1.25 Inch Variable Polarising Filter is a high quality anodised aluminium, optical glass variable polarising filter designed to reduce the amount of light entering your eyepiece. You can progressively dim the view when observing a bright object, such as the Moon or certain planets, to a level according to your needs, whilst increasing contrast, reducing glare and increasing the amount of detail that can be studied. The light transmission can be varied from 40% down to as little as 1%. The filter will not change the colour of the object being viewed and will prevent eye fatigue and loss of night vision.