Optimized for use on fast astrographs for astrophotography and imaging, the Alpine Astronomical Baader f/2 Highspeed Sulfur II Filter isolates this narrow 673nm wavelength to improve the visibility and contrast of faint and wispy emission nebulae, even in heavily light-polluted areas. This filter is ideal when used on Celestron's Rowe-Ackermann Schmidt Astrograph (RASA), or with Hyperstar-equipped Cassegrains.
When conventional narrow-band filters are used on fast optical tube assemblies, there is usually significant transmission loss due to strong center wavelength shift. To counter this, the Highspeed Sulfur II Filter is designed to be pre-shifted to bring them back on-band when used with f/2 to f/3 optical systems. The filter surface is dielectrically coated with anti-reflection coatings to transmit the maximum amount of light throughput and precision polished planeoptically to limit distortion and color fringing. This version of the filter is offered here mounted in a standard eyepiece filter frame for easy installation on just about any 1.25" eyepiece, diagonal, or Barlow lens for prime-focus or eyepiece projection photography and imaging techniques.