Premium light-pollution killer! Celestron"s 2-inch, ultra high-contrast, light pollution reduction (UHC/LPR) filters make deep-sky observation and astrophotography possible in urban areas. That means you can capture stunning views of the Orion Nebula, the Rosette Nebula, the North American Nebula, the Veil Nebula the Helix Nebula, and many, many others from a nearby parking lot! Advanced Technology LPR filters work by reducing transmission of light wavelengths produced by artificial light. This includes mercury-vapor, and both high- and low-pressure sodium-vapor lights. They also block ""sky glow,"" or unwanted natural light, caused by neutral oxygen emission in our atmosphere. While blocking unwanted light, Celestron LPR Filters permit transmission of more desirable wavelengths, including those of hydrogen alpha, hydrogen beta, doubly ionized oxygen and singly ionized nitrogen. This will improve viewing of emission nebulae, both from urban and rural areas. This new, ultra high-contrast (UHC) LPR filter has improved contrast over the typical broadband filters. Sky background is darker, and contrast of emission nebulae is noticeably improved. Advanced-technology coatings enable the filter to achieve outstanding transmission of more than 97 percent across the entire bandpass, with total blockage of prominent light-pollution lines. Celestron"s 2-inch UHC/LPR filter is the perfect accessory for viewing nebula from light-polluted skies, or for boosting the contrast of nebula from dark-sky sites. That makes it a must-have accessory for urban stargazers! * Light Pollution Reduction Filter * Darker Sky Background * Enhances deep sky objects * 2 Inch Format - Threads to bottom of 2 inch eyepieces