H-ALPHA 7nm SQUARE (50x50x3mm)
CCD imagers will find Baader's new Narrowband CCD passfilters to deliver the absolute highest contrast deep sky images in H-Alpha, H-Beta, Oxygen III, and Sulfur-II, with the shortest exposures possible. Their ultra-narrow bandwidths have extremely high transmissions, while completely rejecting light pollution as well as the important blocking of longer wavelengths.
The high optical quality of the Baader narrowband filters guarantees no loss in sharpness or contrast. Each substrate is fine-optically polished plane parallel to deliver a smooth and accurate 1/4 wavefront over the entire surface. This special custom polishing operation sets Baader filters apart from the standard commercially precision polished filter substrates used by most other filter manufacturers.
In addition to their special transmission properties, the Baader coatings were developed with another key goal in mind - eliminate the annoying reflections present in other astro-filters. To achieve this freedom from reflections, along with excellent out of band blocking, required careful design and testing of the coating stacks.
Coatings are professionally applied in Germany by the most sophisticated equipment available today, ensuring high consistency for bandpass centering, transmission, and out of band blocking. The anti-reflection coatings are designed to prevent halos and balanced to prevent deformation of the substrates. The ultra-hard ionbeam deposition ensures the coatings will never degrade from use or normal cleaning.
These filters are available in three sizes, standard 1¼", 2", and a 50.8mm diameter bare substrate (unmounted) for use in SBIG STL cameras. A new unmounted 50.8mm square version of the H-a filter is now available for large format cameras.