The 1.25" Alpine Astronomical Baader Methane Filter passes the near-infrared methane wavelength centered at 889nm with a narrow 8nm bandpass. It is excellent for imaging gas giants such as Jupiter, Saturn, and Neptune.
Using the filter causes features of planets that are dominated by methane to have greater contrast and it makes it easier to image changes. A planeoptically polished Schott RG 830 optical glass substrate and dielectric multi-coatings ensure the precision of the bandpass for optimal image quality. Imaging through the filter will require longer exposure times than normal due to the darkening caused by the band absorption, and since the human eye cannot see wavelengths above 700nm this filter will not add anything to visual observations. Alpine recommends the use of an IR-sensitive CCD camera or webcam and at least a 5" aperture telescope—with 8" recommended. The filter is mounted in a standard 1.25" eyepiece filter housing.