To achieve the desired light attenuation, one or more neutral density filters can be placed in the path of the beam.
A neutral density filter can increase the contrast and cut down the brightness, making the moon easier to view.
Conversely, the flatter its curve becomes, the closer the gel is to a neutral density filter.
A scientific grade neutral density filter can be used to compensate for the over-exposure.
If you want to use large apertures in bright light, a set of neutral density filters is also a nice addition.
A rotating behind-the-lens filter wheel, for selecting an 85A and neutral density filters.
The system allows filters such as rectangular graduated neutral density filters which are versatile in use.
If light levels are high the use of neutral density filters will reduce the light entering the lens, thus enabling the exposure to be extended.
Recent instrumentation has replaced the angled mirror with an inverted microscope and a neutral density filter.
Neutral density filters should then be interposed to reduce light intensity.