Rollei Astroklar Round Filter It is not a coincidence that large reflector telescopes are positioned on mountain summits or remote islands - far away from cities and populated areas. If these telescopes were closer to city centres or towns, it would be almost impossible to see the stars, planets and other celestial objects because of the ever-increasing problem of light pollution. The same is true for photographers who want to take pictures of the city skyline at night and astrophotographers capturing the Milky Way. The new Rollei Astroklar Round Filter is ideal for both professional and amateur photographers. The special anti-light-pollution coating on the filter helps to reduce the unwanted effect of light pollution by filtering out orange and yellow wavelengths, resulting in much cooler, clearer images. To ensure the correct tone in your images, you should therefore use a manual white balance in order to balance the effect of the Astroklar filter. We recommend that you select a colour temperature between +700K and +1, 500K of the white balance that was accomplished without a filter in order to obtain authentic colours in the final result Furthermore, the filter helps to create more contrast between illuminated buildings and the night sky so that even barely visible stars can appear clearly in night images. The Rollei Astroklar Round Filter is available in the following lens diameters; 39, 40.5, 46, 49, 52, 55, 58, 62, 67, 72, 77, 82, 86, 95 and 105mm