SII 3nm Bandpass optimized for f/2.8-f/3.6

$345 ~~$575~~ In stock

Description

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). Chroma’s f/3.0 filters are designed to minimize spectral shift and hold their shape better in an f/3.0 beam.

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Customer Reviews (5.0 / 5 · 5 reviews)

Lily ★★★★★ Oct 21, 2026

The narrowband performance at f/3 is fantastic—finally getting clean SII data without halos around bright stars. Paired with my Ha filter, the nebula details really pop now.

Ellie ★★★★★ Oct 20, 2026

Clear separation of the sulfur doublet at 671.6 and 673.1 nm, even at f/3.2, which surprised me—the stars stay tight and the nebula detail pops without halos. Definitely the sharpest narrowband filter I've used for dim emission regions.

Harper ★★★★★ Oct 19, 2026

I've been shooting the Orion nebula with my f/3 telescope, and the doublet lines at 671.6 and 673.1 nm come through clean without any halos. The contrast against the background is noticeably better than my old 5nm filter.