Astronomik Filters HSO 12nm 2" (85949)

H-alpha Filter: This filter is designed for photographing hydrogen nebulae, whether you are in areas with artificial light pollution or under dark skies. It significantly boosts the contrast between H-alpha emitting objects and the sky background.

With its narrow 12 nm half-width and nearly 100% transmission at the H-alpha line, this filter provides a much greater contrast increase than broadband filters. The 12 nm half-width is ideally suited for typical CCD and CMOS sensors.

Even in large cities, images taken with cooled CCD cameras are usually limited by dark current, so making the filter even narrower does not necessarily reveal more detail. The H-alpha 12 nm filter also has the advantage of making it easier to find tracking stars for most cameras with built-in tracking sensors. The MFR coating technology allows this filter to be used on all instruments with an aperture ratio down to f/3. Astronomik H-alpha filters are not suitable for solar observation.

SII Filter: The SII filter is designed to increase the contrast between sulfur emission regions and the sky background. It has a 12 nm half-width and nearly 100% transmission in the SII line, offering much greater contrast than broadband filters. This filter is also optimized for CCD and CMOS sensors. Like the H-alpha filter, it makes it easier to find guide stars for cameras with built-in tracking sensors.

OIII Filter: This narrowband filter is tuned to the OIII line at 500.1 nm and is suitable for both observation and imaging of OIII regions from light-polluted or dark locations. The OIII filter increases the contrast between certain astronomical objects, such as supernova remnants and planetary nebulae, and the sky background. Its narrow half-width and high transmission make it more effective than filters with wider bandwidths.

The filter blocks emission lines from mercury and sodium lamps, as well as airglow, while allowing the two OIII lines to pass through with very high transmission. It can be used with telescopes from 150 mm aperture at medium magnification and is compatible with lenses and telescopes of all diameters for astrophotography.

Choosing the Right Half-Width: For dark skies, both DSLR and cooled CCD cameras are limited by the camera’s dark current, not by the sky’s brightness, so an even narrower filter does not always improve detail. The 12 nm filters make it easier to find tracking stars, especially with built-in tracking sensors. The 6 nm filters are best for cameras with very low dark current and strong cooling or for imaging faint objects in highly light-polluted locations. These provide even higher contrast and allow for longer exposures, but may make it harder to find tracking stars.

Summary:

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

• Use 6 nm filters for advanced cooled cameras in high light pollution or for maximum contrast with faint objects.

Specifications

• Half-value width: 12 nm

• Frame: 2"

• Mount material: Aluminium

• Coating: Multiple coatings

• Connection to telescope: 2"

• Number of filters: 3

• Type: Line filter

• Series: HSO