The Baader OIII Visual filter is a 10nm visual narrowband filter designed to accentuate the contrast of emission and planetary nebulae. The high transmission at the Oxygen-III line (502nm) results in a bright, contrasty image in telescopes with an aperture of 6" and larger. The optical surface is fine-optically polished so that there is no loss of sharpness at high magnifications, even when the filter is positioned far in front of the focal point. They can even be put in front of a binoviewer without introducing astigmatism. Available in either 1.25" or 2" mounted. The filter cell is threaded on both ends so that multiple filters can be stacked. All Baader filters (excluding 100 x 100mm) come in stackable labelled filter boxes which can be attached to each other to form a sturdy filter library. Specifications Transmission range OIII Central wavelength 502 nm Half-bandwidth 10 nm AR-coating Dielectric coating, planeoptically polished Filter thickness 2 mm (without cell), 6 mm with cell Filter size 2" mounted SKU BA2458396
