Visual and planetary filters thread into an eyepiece or diagonal to improve the view of bright targets: Moon and neutral-density filters cut glare, variable polarizers let you set the brightness, and colour filters raise contrast on planetary features such as Jupiter's cloud belts and the surface markings of Mars. For achromatic refractors, the Baader Fringe Killer and Semi APO and the SVBONY SV231 reduce purple colour fringing, while the Baader U-Venus and SVBONY SV183 685nm IR-pass filters are aimed at planetary imaging. Sets such as the Optolong Planetary Filter Kit, SVBONY SV155 and Antares FS2 cover several colours in one purchase; for deep-sky targets, see light pollution and nebula filters.
