Optolong Ha 7nm, OIII 6.5nm & SII 6.5nm Filter Set

The Hubble Palette: 6.5nm/7nm Tri-Band Narrowband Imaging

This filter set is engineered specifically for SHO imaging, where data from the Sulphur-II, Hydrogen-alpha, and Oxygen-III filters are mapped to the red, green, and blue channels of a final image. This technique, made famous by the Hubble Space Telescope, reveals incredible structural detail and color separation in emission nebulae like the Rosette Nebula (Caldwell 49) that are impossible to capture in broadband.

Designed for use with monochrome astronomy cameras or modified DSLRs, each filter isolates a specific emission line, allowing you to capture deep, high-contrast data one channel at a time, even under a bright moon or from a city backyard.

Precision Bandpasses: 7nm Ha, 6.5nm OIII, and 6.5nm SII

The effectiveness of a narrowband filter is defined by its bandpass—the narrower, the better the contrast. The 7nm Ha filter captures the dominant 656nm wavelength present in nearly all emission nebulae. The even tighter 6.5nm bandpasses on the OIII and SII filters aggressively reject light pollution and background star signal, making faint nebular structures stand out dramatically.

• H-Alpha (7nm): Reveals the foundational hydrogen structure of nebulae with maximum signal.
• OIII (6.5nm): Isolates the 500nm blue-green light characteristic of planetary nebulae and supernova remnants, providing crucial detail and color contrast.
• SII (6.5nm): Captures the deep red light from ionized sulfur, often tracing shock fronts and dense regions that differ from the Ha data.

Advanced Coatings for 1.25", 2", and 36mm Formats

Optolong utilizes an advanced ion-assisted deposition coating process across all filter sizes, ensuring durability and scratch resistance. This technology also provides a stable central wavelength (CWL) that does not drift with temperature changes during an imaging session, preventing signal loss.

This meticulous manufacturing process results in excellent transmission at the target wavelengths and high optical density outside the passband. The coatings are engineered to significantly reduce halos around bright stars, a common issue in narrowband imaging, particularly noticeable in the improved OIII filter performance.

Optolong 6.5nm/7nm SHO Set vs. Wider Narrowband Filters

While wider filters, such as 12nm variants, can be a more forgiving starting point, the Optolong 6.5nm/7nm set offers a significant step up in imaging capability. The primary advantage of the tighter bandpass is superior contrast and the ability to resolve finer nebular details.

The trade-off is that these filters require longer individual sub-exposure times to gather the same amount of signal as a wider filter. However, because they reject so much more background noise, the final integrated image achieves a much higher signal-to-noise ratio, producing cleaner, sharper, and more detailed results from any location.