Agena 2" Color / Planetary Filter - #80A Medium Blue

Color filters can be very useful for enhancing your views of the Moon and the planets. Depending on the atmospheric conditions, the telescope being used, the observer's experience, and the planet being observed or photographed, the advantages of color filters can be anywhere from subtle to dramatic. The right filter can make all the difference between seeing several small craters in the floor of Clavius on the Moon or not; seeing five or six swirls in Jupiter's belts or not; or seeing the inner Crepe Ring of Saturn or not.

Agena's 2" color/planetary filters are manufactured from the purest optical glass and are dyed-in-the-mass (not simply "color coated") for premium performance. They thread into the barrels of virtually any 2" telescope eyepiece. Each filter cell has a male and female 2" filter thread (M48x0.75) on opposite sides, so multiple filters can be stacked to achieve selective filtration of the visual color spectrum. The clear aperture is 43mm and each filter comes in a protective plastic storage case.

The #80A Medium Blue Filter is one of the most commonly used filters amongst the entire spectrum of filters. It is perhaps the best filter for the study of detail on Jupiter and Saturn. It enhances the contrast of rills and festoons in Jupiter's cloud belts, as well as details of the Great Red Spot. It brings out detail in Saturn's belts and polar features. The filter is very useful on Mars in showing the high clouds and ice caps, and is especially useful during the violet clearing.

When used on Mercury around twilight, it improves the surface markings, whereas for Venus it shows dark shadings in the upper clouds. You can even use it on double stars - try it on Antares, for example. It is also a very useful filter for the Moon. The blue filter also brings out gas tails of comets.