The Celestron RASA filter has sharp cutoff passbands that "surgically" remove the unwanted light pollution at city and suburban observing sites while preserving as much of the useful spectrum as possible. You still retain over 90 percent of the light captured by your telescope at many of the most important wavelengths. The result is the best light pollution suppression filter for astroimaging with the fast f/2.2 focal ratio RASA.
From a dark sky site, the #93617 RASA filter blocks much of the normal atmospheric skyglow that brightens the sky background and reduces contrast in long exposures. Imagers have found a marked improvement in as much as 98% of their exposures from a dark sky site. Whether from a light-polluted city or a dark sky site, with the #93617 filter, your RASA images have darker sky backgrounds with more defined galaxy and nebula detail and contrast.
The 72mm diameter 2.1mm thick mounted filter replaces the placeholder glass in the camera attachment port at the front of the RASA optical optical tube, so that the RASA's precise optical path is unaltered. No matter which camera you use, this filter's generous 68mm clear aperture allows it to easily accommodate today's largest DSLR and CCD sensors without vignetting.
Unlike other light pollution suppression filters, the new Celestron LPR Imaging Filter for RASA maintains a neutral color balance. Dielectric coatings further enhance light transmission, so you can bring out subtle color in galaxies and other faint deep sky objects. Meanwhile, anti-reflective coatings on the Schott B270 optical glass substrate prevent star halos and minimize internal reflections.
While the response curve in the feature image above shows a response range from 400 nm to 750 nm, the filter actually has 100% blocking out to 300 nm in the UV and 1100 nm in the NIR. This means that no additional UV/IR cutoff filters are needed for optimum performance.
Every Celestron #93617 RASA Light Pollution Imaging Filter is tested individually for light transmission. Inside the box, you'll receive the actual transmission spectrum for your specific filter. Your report is prepared by Astrodon and matched to your filter's serial number, so you can have total confidence in your filter's performance.
