High Point #38A Dark Blue Filter - 1.25" - 38AF1

This High Point Colored Filter has a Wratten number of #38A, which is Dark Blue with a transmission of 17%. A blue filter is useful for Great Red Spot on Jupiter, or to enhance the boundaries between the giant planet's reddish belts and their adjacent bright zones. A blue filter is also helpful when studying surface features and polar ice caps on Mars, or to improve Mercury's surface markings at twilight, when the elusive planet is low on the horizon. When observing Saturn, a blue filter will enhance low-contrast features, such as those found between the belts and zones. Checking out a comet? Use a blue filter to bring out definition in its gaseous tail.

Colored filters can be an invaluable aid in lunar and planetary observing. They reduce glare and light scattering, increase contrast through selective filtration, increase definition and resolution, reduce irradiation and lessen eye fatigue.

All of High Point's colored filters are made of high quality, solid plane parallel glass that has been anti-reflection coated to prevent glare and ghosting. They have a full 26mm clear aperture, and are mounted in a black anodized aluminum cell that is threaded on both sides to fit most eyepieces and stack with each other.

Please note that the effectiveness of this filter depends on several factors, including the aperture and focal length of your telescope, the magnification being used, and the seeing conditions at the time. Remember that filters lower the amount of light that reaches your eye. You'll need an aperture of at least 8 inches for dark filters such as the #47 Violet, with only 3% transmission, the #25 Red with just 14% transmission, or the #38A Blue with 17% transmission.