By star-shaping light sparkling from light sources like holiday illuminations or water surfaces, star filters can confer your photos a more scenic and impressive effect. In the same way as for C-PL filters, star filters come in a two-filters rotating structure that, by rotating the filter’s frame, allows adjusting the angle of the light rays hitting the filter’s surface.
A little trick when shooting with these filters will be to not narrowing the aperture too much: when shooting with a high aperture value of f/16 or f/22, light rays will be cut short, thus restricting star filters' special effect.
In addition to the most popular 4-point type, star filters' lineup includes 6-point and 8-point types as well, and can be effectively used with any standard lens.
Also, follow the article on how to use star filters to capture city illuminations.