This 20nm filter replaces the former, and popular, 35nm H-alpha filter, which was developed for interline CCD cameras. Due to advances in sensor technology, now much narrower filters can be used with colour sensors.
Compared to the CMOS-optimized Baader (Ultra) Narrowband Filters, the 20 nm H-alpha filter passes considerably more light. This makes the stars in the image brighter, allowing easier focusing, and the filter can be used at all focal ratios: There is no need for preshifting as with narrow band filters. This filter is especially interesting for users of colour cameras (which are less sensitive to red than monochrome cameras) who do not need extreme narrowband filters and want to enrich their colour images with H-alpha. At the same time this filter is a valid alternative to a standard R-filter of the RGB-scheme. It blocks much more of deteriorating light pollution and still passes all H-alpha for all focal ratios. Warning: this filter alone is not suitable for direct viewing of the sun!
A notable difference to all H-alpa pass filters on the market is the fact that this filter does include highly efficient UV/IR blocking. being completely blocked out to 1400 nm, to eliminate blurring (“heat-noise”) caused by defocused light on refractor optics.
The Baader H-alpha Bandpass (20 nm) filter has got all the advantages of the new generation of CMOS-optimized Baader filters:
- Increased contrast, matched for typical CMOS quantum efficiency and s/n ratio
- Reflex-Blocker™ coatings, for largest ever freedom from halos, even under most adverse conditions concerning aux-optics
- Identical filter thickness to existing standards, with utmost care for parfocality
- Blackened edges all around, with filter-lead-side-indicator in the form of a telescope-sided black outer rim, to additionally eliminate any reflection due to light falling onto the edge of a filter, making additional front-masks obselete.
- Each filter coated individually, with sealed coating edge (NOT cut out of a larger plate with coatings left exposed, read more)
- Life-Coat™: evermore hard coatings to enable a non-aging coating for life – even in a most adverse environment