This Celestron Light Pollution Imaging Filter is specifically designed for the RASA 8-inch telescope. We all know how much of a problem light pollution can be, and this filter selectively blocks the wavelengths of light from streetlights and general city lighting, but not broad regions of the spectrum. You can rest easy knowing that it will not block any of the wavelengths you want and need in order to image nebulae, galaxies, and more. This filter fits snugly into the RASA's integrated filter mount and its flat surface is free of defects and constructed of Schott glass with anti-reflection coatings.
The Solution to Light Pollution
Light pollution in the night sky significantly degrades contrast in astronomical images. This is especially true when using very fast telescopes like the 8-Inch RASA because the sky background saturates very quickly. The "noise" of the light pollution overwhelms the "signal" from the celestial object you are imaging, making it difficult to get the most detailed image. The Light Pollution Imaging Filter for the 8-inch RASA remedies this by blocking light pollution while transmitting light from deep-sky objects. The result is bright, detailed objects that pop 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 wavelengths, the filter greatly reduces the effects of light pollution without degrading overall image quality.
Celestron's Light Pollution Filter Transmissions
This Light Pollution Imaging Filter for the 8-Inch RASA blocks light from some of the most common sources of light pollution between 400 to 700 nm (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 color balance. In addition, specific wavelengths associated with emission nebulae, such as H-a (656 nm), H-b (486 nm), OIII (496 nm and 501 nm), and SII (672 nm), 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.
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