Coloured filters can be used to bring out details on a planet's surface or its cloud structure. All of the planetary filters included in the Celestron Lunar and Planetary Filter Set can be used on any 1.25" eyepiece with the proper filter threads, so they are very versatile. Just screw one onto the eyepiece of choice and slide it into the focuser.This Celestron filter set includes the following colours:12 Deep Yellow - A good general purpose filter for smaller aperture telescopes (less than 4.5"), the 12 Yellow will improve the contrast of features on the Moon. It will also help you see the equatorial belts on Jupiter and Saturn, clouds and the polar ice caps on Mars, and the dusky detail on Uranus and Neptune.21 Orange - Sharpens the boundaries along the plains of Mars due to the reduction of blue/green transmissions. Use on Jupiter and Saturn to enhance detail in the belts and polar regions.80A Blue - Enhances the contrast of the cloud belts on Jupiter and the polar ice caps on Saturn. It also can be used to increase contrast on the Moon if you don't mind the colour shift.ND-96-0.3 Neutral Density - A great filter for the Moon, and for stacking with other planetary filters to increase density without changing the colour. A neutral density filter is also useful when splitting binary star systems (double stars). Use anytime you want to decrease brightness but don't want to affect the color characteristics of an object.Each Celestron 1.25" filter has 26mm of clear aperture, and is mounted in a black anodised aluminum cell that is threaded on both sides. Double threads allow the user to stack different filters together to create a custom colour or affect the transmission percentage. Special coatings on each filter protect against reflections, ghosting, and scratches. A plastic case is included to keep your filters safe when not in use.Features- A nice beginner's set of 1.25" planetary filters for any telescope.- See features on the Moon & planets in a whole new light.- The aluminum cell is threaded on top and bottom for stacking.- Includes Wratten 12 Deep Yellow, 21 Orange, 80A Light Blue, and a ND-96-0.3 Neutral Density Filter with 50% transmission.