Grey filter with 13%, 25% and 50% transmission. If you want to observe the moon with large aperture telescopes, you will usually need a relatively dark moon filter, so sufficient absorption is present with very large apertures. These filters are recommended starting from an aperture of 200mm, and especially with 250mm or above.
ND = Neutral Density %
Lumicon filters use ND as a light transmission percentage. ND13 is hence equivalent to a 13% light transmission, ND25 to a 25% light transmission and ND50 to a 50% light transmission. So, for example, an ND25 filter allows more light to pass through than an ND13.
|Connection (to the telescope)||2"|
|Transmission||13, 25, 50%|
|Coating of optical system||multiple|
|Type of build||neutral density filter|