Filters CLS RASA Origin

The CLS (City Light Suppression) broadband filter was developed to improve the visibility of a range of deep sky objects

Emission nebulae emit primarily at certain wavelengths of light - Hα at 656 nm, Hβ at 486 nm and OIII at 496/501 nm. By allowing only these wavelengths of light through and virtually blocking the rest, the filter dramatically reduces the effects of light pollution. The "bad" light is blocked while the "good" light is allowed through.You will immediately notice a much higher contrast in your images, especially in locations with light pollution!

Why does the RASA Origin require a special CLS filter?

Other filters on the market that are designed for colour cameras have much narrower transmission windows at the critical wavelengths. Unfortunately, these filters block most of the incoming Hα-Hβ-OIII light on an f/2.2 optical system such as the 6" RASA. This is because a RASA brings the light into the filter at a steeper angle, causing a spectral shift. If you use filters that are not specifically designed for use at f/2.2, some of the light will be blocked, resulting in a weaker image. The nebulae filter for Origin has been specially designed for use at f/2.2, so that the desired spectral lines are not accidentally blocked by the filter.