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High Point #25 Red Filter - 2" - 25F2


High Point #25 Red Filter - 2"

This High Point 2" Colored Filter has a Wratten number of #25, which is Red with a transmission of just 14%. A red filter will help with daytime observations of Venus and Mercury by darkening the blue sky. When observing Jupiter and Saturn, you can expect a red filter to help you study clouds that have a bluish hue. Mars will also benefit from a red filter in several ways. It will enhance polar ice caps as well as surface details, and will also sharpen the boundaries of yellow dust clouds.

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 2" 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 43mm clear aperture, and are mounted in a black anodized aluminum cell that is threaded on both sides to fit most 2" eyepieces and stack with other High Point 2" filters.

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.