Astronomik Filters HSO 12nm 1,25" (85948)

H-alpha Filter: This filter is designed for photographing hydrogen nebulae both in areas with artificial light pollution and at dark-sky locations. It significantly enhances the contrast between H-alpha emitting objects and the sky background. With a narrow half-width of 12 nm and high transmission close to 100% in the H-alpha line, it provides much greater contrast than broadband filters. The 12 nm half-width is optimized for typical CCD and CMOS sensors.

Even in large cities, images taken with cooled CCD cameras are generally limited by dark current rather than sky background. Therefore, using a filter with an even narrower half-width does not reveal more details. Compared to ultra-narrowband filters, the H-alpha 12 nm filter makes it easier to find tracking stars for most cameras with built-in tracking sensors. The advanced MFR coating allows use with optical systems down to f/3. Astronomik H-alpha filters are not suitable for solar observation.

SII Filter: The SII filter increases the contrast between sulfur regions and the sky background. It also features a narrow 12 nm half-width and high transmission close to 100% in the SII line, ensuring greater contrast than broadband filters. Like the H-alpha filter, the 12 nm version is ideal for typical CCD and CMOS cameras, and helps users find suitable guide stars for autoguiding.

OIII Filter: The OIII filter is intended for both observing and photographing OIII regions, suitable for use under light-polluted or dark skies. It increases the contrast between objects such as supernova remnants and planetary nebulae and the background. With a narrow half-width and high transmission in the OIII line, it outperforms filters with wider bandwidths. The filter can be used with telescopes from 150 mm aperture at medium magnification and is compatible with all lens and telescope diameters for astrophotography. It completely blocks the emission lines from mercury and sodium lamps, as well as airglow, while allowing the two OIII lines to pass with high transmission.

Choosing the right half-width: Under dark skies, DSLR and many cooled CCD camera images are limited by the camera’s dark current, not by sky background. In such cases, a smaller half-width will not reveal more object detail. The 12 nm filters are easier for finding tracking stars, especially with cameras that have built-in tracking sensors. The 6 nm filters are recommended for cameras with very low dark current and strong cooling, or for locations with high light pollution, as they offer even stronger suppression of sky brightness and higher contrast for faint objects, though tracking stars may be harder to find.

In summary:

• Use 12 nm filters for DSLRs and cameras with higher dark current.

• Use 6 nm filters for advanced cooled cameras in heavily light-polluted locations or for imaging very faint objects requiring maximum contrast.

Specifications

• Half-value width: 12 nm

• Frame: 1.25"

• Mount material: Aluminium

• Optical coating: MRF

• Connection to telescope: 1.25"

• Number of filters: 3

• Type: Line filter

• Series: HSO

Area of Application

• Useful for photographs: Yes

• Visually useful: Yes

• Nebulae & galaxies: Yes