Sightron - Quad BP III Filter Ø 31.7 mm

Comet BP Filter Ø 31.7 mm (1.25")

The Quad BP filters (Quad Bandpass) are interference filters that transmit wavelengths near the four main emission lines of celestial objects - Hα, Hβ, OIII, and SII - and block the rest of the wavelength range.
Since it blocks wavelengths other than those close to the four main emission lines, it should have a strong effect in reducing light pollution. These filters are popular for urban nebula photography and telescope observation using digital SLR and mirrorless cameras.
The classic QBP filter was designed to gradually transmit rays close to infrared above 900 nm, but the new Quad BP Filter III extends the blocked wavelength range to 1,100 nm. When used in combination with achromatic mirrors, it prevents the appearance of halos around bright stars.

Product features

Transmits four emission lines

Mainly transmits the wavelength range around the four main emission lines (Hα, Hβ, OIII, and SII) emitted by celestial objects and blocks other wavelength ranges, making nebulae visible even in light-polluted areas.

Blocks wavelengths up to 1100 nm

Conventional QBP filters were designed to gradually transmit rays from the near-infrared above 900 nm, but when used in combination with achromatic mirrors, bright stars were covered with halos. By extending the cutoff wavelength range to 1,100 nm, the QBP filter prevents the appearance of halos around bright stars when used in combination with achromatic mirrors.

Reliable Japanese quality

As with previous products, this is a reliable Japanese product. A multi-layer film is deposited on both sides of the high-precision polished glass substrate by IAD (Ion Assisted Deposition) by a major Japanese manufacturer. The film surface has high density, homogeneity, and stability.

Universal thread diameter 31.7 mm (1.25")

Standard diameter of Ø 31.7 mm that can be used with many telescopes.

Examples with Comet BP and Quad BP filters

In the case of galaxies and star clusters emitting light in a continuous spectrum, the Comet BP filter is capable of producing richer and more natural colors than the Quad BP filter, which only transmits four emission lines.

Sky-Watcher BKP130OTAW Image Collector F5 / ISO3200 180s / with white balance and exposure compensation

Differences between Comet BP filters and Quad BP filters

Although the Quad BP filter is superior in terms of its ability to reduce light pollution, the Comet BP filter excels in rendering colors more naturally. It is particularly recommended for objects that require a natural representation of colors, such as galaxies, star clusters, and reflection nebulae that emit light in a continuous spectrum.

.

We recommend using the Quad BP filter for imaging in urban areas where light pollution is particularly significant or for emission nebulae, and the Comet BP filter for comets and galaxies.