Ban light pollution
You want your telescope to gather light from the sky, not from city lights and other artificial sources. The Celestron UHC (ultra high contrast) light pollution reduction filter selectively reduces transmission of those distracting wavelengths of terrestrial light, for a vast improvement in your night-sky viewing experience. Advanced technology coatings allow the filter to achieve an outstanding transmission of over 97% across the entire bandpass, with total blockage of prominent light pollution lines. That means better viewing of nebulae through light polluted skies, or a nice boost in contrast when viewing nebulae from dark sky sites. It's a must-have for deep-sky photographers.