of solar features, especially sunspots and granulation on the surface, as well as solar eclipses and transits of the inferior planets Mercury and Venus across the solar disk. Narrowband filters The Herschel Wedge is a prism-based device combined with a neutral-density filter that directs most of the heat and ultraviolet rays out of the telescope, generally giving better results than most filter types. The H-alpha filter transmits the H-alpha spectral line for viewing solar flares and prominences invisible through common filters. These H-alpha filters are much narrower than those use for night H-alpha observing (see Nebular filters below), passing only 0.05 nm (0.5 angstrom) for one common model, compared with 3 nm-12 nm or more for night filters. Due to the narrow bandpass and temperature shifts often telescopes like that are tunable within about a ±0.05 nm. NASA included the following filters on the Solar Dynamics Observatory, of which only one is visible to human eyes (450.0 nm): 450.0 nm, 170.0 nm, 160.0 nm, 33.5 nm, 30.4 nm, 19.3 nm, 21.1 nm, 17.1 nm, 13.1 nm, and 9.4 nm. These were chosen for temperature, instead of particular emission lines, as are many narrowband filters such as the H-alpha line mentioned above. Color filters Color filters work by absorption/transmission, and can tell which part of the spectrum they are reflecting and transmitting. Filters can be used to increase contrast and enhance the details of the Moon and planets. All of the visible spectrum colors each have a filter, and every color filter is used to bring a certain lunar and planetary feature; for example, the #8 yellow filter is used to show Mars's maria and Jupiter's belts. The Wratten system is the standard number system used to refer to the color filter types. It was first manufactured by Kodak in 1909. Professional filters are also colored, but their bandpass centers are placed around other midpoints (such as in the UBVRI and Cousins systems). Some of common color filters and their uses are: Chromatic aberration filters: Used for reduction of the purplish halo, caused by chromatic aberration of refracting telescopes. Such halo can obscure features of bright objects, especially Moon and planets. These filters have no effect on observing faint objects. Red: Reduces sky brightness, particularly during daylight and twilight observations. Improves definition of maria, ice, and polar areas of Mars. Improves contrast of blue clouds against background of Jupiter and Saturn.