This uses the old etalon design and will sell until out of stock. New options available on the site. The Lunt LS60FHa is a 60 mm aperture (no central obstruction) integrally tuned etalon for use on a customer supplied refractor. A B600 blocking filter provides full disk images on telescopes up to 540 mm focal length. Larger blocking filters suitable for longer focal length telescopes are also available options. Choose the filter/blocking filter package that is suitable for your telescope and your focuser size: B600 – Up to 540 mm focal length, offered in 1.25" or 2" diagonal B1200 – Up to 1080 mm focal length, offered in 1.25" or 2" diagonal B1800 – Up to 1620 mm focal length, offered in 1.25" or 2" diagonal B3400 – Up to 3060 mm focal length, offered in 2" straight-through tube This Hydrogen-alpha filter is designed to retrofit (adapters required) a customer-supplied telescope for use during the day. It is easily removable so that the scope can continue to be used for night observing. Because the LS60FHa H-Alpha Filter has an estimated bandpass of