Lunt LS40F Hydrogen-Alpha Front-Mounted Etalon System B1200

The LS40F brings hydrogen-alpha solar observing within reach. This 40mm front-mounted etalon converts your existing refractor into a capable solar telescope, revealing prominences, filaments, active regions, and chromospheric detail at a price point that makes H-alpha accessible.

The LS40F uses a center-supported etalon design—an approach with proven heritage in solar filtration—paired with precision tilt tuning for smooth wavelength control. The design delivers a <0.65 angstrom bandpass: tight enough for rewarding views of solar activity, and an excellent foundation for observers ready to explore the chromosphere.

Each system ships complete with a B1200 blocking filter (6mm clear aperture, for focal lengths up to 540mm) and a custom adapter plate machined to fit your telescope. Provide your objective cell diameter when ordering, and we'll include the correct adapter at no charge—accommodating refractors with objective housings up to 4 inches.

Remove the system in seconds to return your refractor to nighttime duty.

Technical Note: This system is designed with a center-mounted foot to support the etalon. Consequently, the filter is center-obstructed.   

Specifications:

• 40mm etalon with center-supported design (Note: Filter is center-obstructed)
• <0.65 angstrom bandpass (H-alpha, 656.28nm)
• Tilt-tuned wavelength control
• B1200 blocking filter included (6mm CA, up to 540mm FL)
• Custom adapter plate included (up to 4" objective cells—specify diameter at checkout)
• Visual and imaging capable