Celestron Narrowband H-Alpha/H-Beta/OIII Imaging Filter for 8-Inch RASA

Bring out the best in your nebulae astroimages with the H-alpha H-beta OIII (Ha-Hb-OIII) Imaging Filter for the 8-inch RASA. This specialized filter 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. You’ll notice much higher contrast in your images immediately, even if imaging from your light-polluted backyard! And since the transmission at the key wavelengths is so high, the nebula will not be dimmed—only the background will be blacker.

Nebula Hunting

The H-Alpha/H-Beta/OIII Imaging Filter for the 8-inch RASA is perfect for imaging emission nebulae like the North America Nebula (NGC 7000), Lagoon Nebula (M8), Orion Nebula (M42), and the Carina Nebula (NGC 3372). The imaging filter transmits key H-Alpha/H-Beta/OIII wavelengths that produce high contrast for emission nebulae. The transmission spectrum for the Imaging Filter is 85% or greater at key wavelengths (486nm, 496nm/501nm, 656nm) and less than 0.5% transmission elsewhere. The Imaging Filter for the 8-inch RASA is a narrowband filter that blocks much of the visible spectrum and only lets specific wavelengths through. Because of this, it will not work well on broadband emission objects, such as galaxies and star clusters. The Celestron Imaging Filter for the RASA 8 was custom engineered to work at F/2, so none of the “good” light from the nebula is inadvertently blocked by the filter.

Body and Storage

The filter is machined aluminum black anodized cell with knurled rim for easy grip during installation. An anti-reflection coating has been added to the filter to help suppress reflections on the glass. 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. No other adapter is needed.