Baader f/2 Highspeed Narrowband Filters and Filtersets.
Available in 31mm, 1.25" and 2" sizes, H-alpha, OIII and SII. These filters are designed especially for the delicate requirements of extremely fast astrograph optics, in particular Hyperstar and Celestron's New Rowe-Ackermann Astrograph (RASA).
Conventional narrowband filters cause a heavy loss in transmission due to the strong center wavelength (CWL) shift. In extreme cases the CWL shift can cause a shift of the full width half maximum (FWHM).
The Baader highspeed narrowband filters have a CWL preshift which matches f/2 to to f/3.5 and the FWHM is also optimised. They are planeoptically polished and hard coated.
Despite the typical line broadening with such fast optical trains they are able to deliver maximum contrast. For the first time these filters allow the effective use of fast optics with high contrast emission nebulae imaging.
Using these filters when imaging between f/1.8 and f/3.5 shows a dramatic improvement compared to any regular set of narrowband filters.
H-alpha (Hydrogen Alpha)