Please Note:The interference coatings that optical filters are made with are angle-sensitive and shift to the blue with fast focal ratios. This is not a problem for filters 5nm or wider, but the 3nm filters shift enough to compromise transmission at the wavelength line of interest. Chroma has made a set of Ha, OIII and SII 3nm that are optimized for F/3 beams by moving the center wavelength slightly into the red so they will shift slightly to the blue when used in an F/3 beam, thus maximizing transmission at the nominal wavelength. For beams faster than F/3, we recommend using 5nm-wide or wider bands.
Best in Class Filters
Chroma filters are widely recognized as being some of the best in astrophotography. The versatility of Chroma manufacturing is also highlighted in these filters designed for fast telescopes, separate to the standard filters they produce as well. No matter what kind of imaging you're planning for, these American made filters are sure to satisfy any imager's needs.
Made in the U.S.A.
Designed and manufactured here in the U.S.A., you can be sure that these filters will be up to par with the extreme quality control required for astrophotography. On top of this, buyers here in the U.S.A. will not have to wait long at all to receive their filters--so long as they're in stock, that is! The immense popularity of Chroma brand filters keeps the company at peak performance to maintain supply for an always increasing demand.
Chroma SII 3nm Narrowband Filters are essential for imaging objects, like nebulae, that are rich in ionized sulfur atoms. These line emission filters work extremely well in heavy light polluted areas and allow you image on nights when the moon is up.
SII filters isolate the spectral emission of singly ionized sulfur atoms, also common in nebulae. Emission is at two lines occurring as a doublet, at 671.6 and 673.1 nm. This filter also separates sulfur emission from H-alpha emission (656.3nm).