Filters Filter Set Moon & Planets from 150mm Telescopes 1.25"

Color filters are an essential tool of the lunar and planetary observer, for filters permit the observation and photography of surface detail that is often virtually invisible without filtration.

Filters solve, or greatly reduce the effects of, two basic observing problems: (a) Irradiation is the fuzzying of a boundary between lighter and darker areas of the Moon or a planetary surface and can be caused either by the effects of highly contrasting light impacting the human eye or by the motion of the Earths atmosphere, through which the observation is being made. (b) Contrast is the separation of adjacent surface regions according to their color; for example, a light green area on Mars can become mixed in the eye with an adjacent light yellow area, to the effect that the combined area appears yellow-green, unseparated into its component regions.

The use of a color filter can mean the difference between seeing small craterlets in the floor of Clavius on the Moon and not; it can mean the difference between seeing five or six whirls, festoons, and loops in Jupiters north equatorial belt and seeing one or two; it can mean the difference between seeing the inner crépe ring of Saturn and not. Depending on atmospheric conditions on both the Earth and the planet being observed, the advantages of color filters can be anywhere from subtle to dramatic.