Chroma SHO (S-II, H-a & O-III) 3nm Imaging Filter Set - 50x50mm Square Unmounted
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About Chroma Filters
Chroma produces premium astronomy filters using durable sputtered hard coatings on single high-quality glass substrates, avoiding laminations. Primary coatings are applied to the front surface, with anti-reflection coatings on the rear to suppress ghosting and maximize throughput. Their filters maintain stable, precise passbands that do not drift with temperature or humidity changes and are optimized for optical systems of f/4 or slower.
Cleaning, Handling, and Orientation
Handle Chroma filters only by their edges. Clean sparingly and only when needed. Remove loose particles with a bulb puffer or filtered compressed air. If deeper cleaning is required, gently wipe the surface with anhydrous alcohol and lint-free laboratory wipes, using a fresh section of the wipe for each pass.
SII filters isolate the emission from singly ionized sulfur, a key component in many nebulae. These emissions occur as a closely spaced doublet at 671.6 nm and 673.1 nm. This filter cleanly separates sulfur emissions from the H-alpha line at 656.3 nm.
H-alpha filters are critical for capturing nebulae and other hydrogen-rich objects. Centered at 656.3 nm, this narrowband filter isolates H-alpha light from the nearby SII doublet (671.6 nm and 673.1 nm), boosting contrast and revealing fine structural detail.
O-III filters target the dominant 500.7 nm emission line of doubly ionized oxygen, the second most common spectral line in nebular imaging after H-alpha.
The glass substrate is 3 mm thick.