Compact SVBONY 1.25 CLS Filter for Deep Sky Astrophotography

The City Light Suppression broadband filter, designed by the brand Observation Discovery & Exploration, is intended to enhance the visibility of various deep-sky objects. This filter selectively reduces the transmission of wavelengths associated with light pollutants, such as those produced by artificial lighting, including mercury vapor lamps, high and low-pressure sodium vapor lights, and the unwanted natural light caused by neutral oxygen emission in the atmosphere, like sky glow.

The Planetary rotation system offers precision and homogeneity of coatings, ensuring high value on the transmission of the pass-band and optical density of the off-band. This ultra-thin filter cell minimizes vignetting, providing a 90% transmission of the main nebula emission lines, including H-alpha 656nm, OIII 496nm & 500nm, SII 672nm, and H-beta 486nm. Additionally, the filter achieves a 0.1% transmission of off-band wavelengths, specifically the major emission lines of artificial light pollution, such as Na 589nm, Hg 435nm, and 578nm.

Crafted with an evaporation with Ion-assisted deposition coating technology, the filter boasts durability, resistance to scratching, and stability in its central wavelength, unaffected by temperature changes. The CLS filter is compatible with color CCD cameras and unmodified DSLRs, making it a versatile tool for both visual and photographic deep-sky observations.

Unlike filters that eliminate the effects of light pollution or increase the object's brightness, the CLS filter aims to enhance the contrast between the nebula and the night sky, without necessarily brightening the nebula itself. This feature is particularly beneficial for observations in sub-rural areas with mild to moderate light pollution.

It is essential to note that the SVBONY filters are not designed for sun observation, and users should never look directly into the sun with these filters, as it can result in eye damage.

The CLS filter's specifications include an optical glass lens, an aluminum frame, and a round shape with a 1.25-inch barrel diameter and a standard M28.5 x 0.6mm thread. The net weight of the filter is 5.2g / 0.18oz, and the glass thickness is 1.85mm.

In summary, the City Light Suppression broadband filter from Observation Discovery & Exploration is a versatile and effective tool for enhancing the visibility and contrast of deep-sky objects, particularly in areas with mild to moderate light pollution. Its precise coating technology, compatibility with various imaging systems, and selective wavelength filtration make it a valuable addition to the arsenal of astrophotographers and visual observers alike.

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