Baader 3.5- 4 nm Ultra-Narrowband 1.25" Filter Set: H-Alpha/O-III/S-II

Baader Ultra-Narrowband CMOS-Optimized Filter Set:
H-alpha, OIII, and SII

This 1.25" filter set is optimized for CMOS cameras, but also ideal for CCD imaging. Included in the set are 3.5 nm H-alpha, 4 nm OIII, and 4 nm SII filters. These ultra-narrowband filters allow for the highest contrast, even in the most light-polluted environments.

With CMOS-optimization in mind, these filters utilize a a coating specifically designed to avoid haloing when used with coma-correctors, field-flatteners, or reducer-correctors.

These filters are constructed with blackened and coating-sealed edges, and recommended for optical systems of f/10 to f/3.5. Each filter comes in its own plastic storage case.

3.5 nm CMOS-Optimized H-Alpha Filter
This ultra-narrowband filter eliminates all but 3.5 nm of the h-alpha emission line, resulting in extremely high contrast astrophotography, minimizing star size and emphasizing fine nebula detail. The central wavelength of its 3.5 nm bandwidth occurs at 656.3 nm. Such a narrowband filter also suppresses mercury (Hg) and sodium (Na) emission lines, which are main sources of light pollution, making this filter good for use under suboptimal skies.

4 nm CMOS-Optimized S-II Singly Ionized Sulfur Filter
The S-II singly ionized sulfur filter allows for extreme contrast at an ultra-narrowband of 4 nm. Centered at a wavelength of 671.7 nm, the 4 nm bandwidth is enough to capture singly ionized sulfur emissions at both 671.7 nm and 673 nm common to S-II.

4 nm CMOS-Optimized O-III Doubly Ionized Oxygen Filter
The O-III doubly ionized oxygen filter also allows for extreme contrast at an ultra-narrowband of 4 nm, but centered around the O-III emission line of 500.7 nm.

Features:

• Premium grade H-Alpha, O-III, and S-II ultra-narrowband filters

• 3.5 nm-4 nm FWHM for optical systems between f/10 to f/3.5

• Very high contrast even under substantial light pollution

• Reflex-Blocker coating

• Blackened edges

• Optimized for CMOS cameras and also suited for CCD