In very nice clean condition and very sort after
Also known as the Horsehead Nebula filter, the Lumicon 1.25" Hydrogen-Beta Filter isolates only the hydrogen-beta line of the spectrum (486nm) in a narrow pass-band just 9 nm wide, providing maximum contrast. Now you can view extremely faint nebulous objects such as the Horsehead, Cocoon and California Nebulae. In many cases, the Lumicon Hydrogen-Beta Filter is the ONLY way to view these objects. Recommended for 8" or larger telescopes.
To ensure that your Lumicon filter remains the World's Best, the strictest quality control standards are employed throughout the production process. Each Lumicon Hydrogen - Beta Filter is individually inspected and proudly inscribed with the percentage of light transmittance of the H-Beta emission line.