Sky Mentor ND4 1.25" Neutral Density Filter This Neutral Density (ND) filter is suitable for 1.25" eyepieces & other 1.25" barreled accessories. Neutral Density filters are preferred as a moon filter due to their neutral color, the ND4 filter can reduce the overall brightness of the moon's surface by 75% (transmission is 25%) so you can see more details and surface features of moon with your telescope, even during its fuller phases. We also offer two other Neutral Density filters with varying degrees of light attenuation: ND2 transmits 52% of the incoming light ND4 (this filter) transmits 25% of the incoming light ND8 transmits 12.5% of the incoming light These filters result in perfectly neutral color will not alter the natural color of the moon. The higher the ND number (2, 4 or 8) the darker the filter and, therefore, the less light it transmits. We recommend you choose the filter that allows for the most comfortable viewing so your eyes will relax and you can see finer details.
