The Celestron Light Pollution imaging filter for the RASA 8" allows high transmission of light from emission nebulae while blocking light pollution, helping to make your images pop with detail off the black sky background with superior contrast. Fortunately, many sources of light pollution have relatively discreet emission spectra; they emit primarily at specific wavelengths of light. By strategically blocking these “bad” wavelengths, the filter essentially eliminates the effect of light pollution while letting the “good” wavelengths of light associated with the emission nebula pass through to the camera. The Light Pollution Imaging (LPI) Filter for the 8” RASA blocks light from some of the most common sources of light pollution between 400-700nm (i.e., the visible spectrum), including high- and low-pressure sodium-vapor streetlights, mercury-vapor streetlights, and natural airglow caused by oxygen in the atmosphere. Unlike some light pollution filters, the LPI filter blocks only specific areas of the spectrum instead of wide regions. This helps to maintain image brightness and colour balance. In addition, specific wavelengths associated with emission nebulae, such as H-a (656nm), H-b (486nm), OIII (496nm and 501nm), and SII (672nm), are highly transmitted, ensuring minimal loss of image brightness for those objects. The filter fits directly into the internal filter mount in the RASA 8’s front lens cell, where the optical window normally mounts. By removing the clear window and replacing it with the filter, optical performance for the entire system is maintained. Each filter comes with a plastic storage case to safely store the filter or the placeholder glass that came with your RASA when not in use. You will also receive a spectral transmission graph unique to your specific unit, verifying its performance. Specifications Clear aperture 43 mm Coatings Dichroic multi-layer AR coatings Filter thickness 1.9 mm (without cell) Filter diameter 46 mm SKU CE-93614
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