ESO Astronomical Glossary - F
Far ultraviolet
See Ultraviolet radiation.
F-star
See Spectral Type.
Filter
A filter is an optical device that blocks certain types of light and transmits others. In astronomy filters are mostly used to study light from a source in one particular colour, i.e. in a particular wavelength region, which can yield information on the chemistry of the object. The information gained from studying the object in several different filters in teh course of an observation can then be combined to produce a more detailed overall picture.