A filter or lens for a star-tracking telescope includes a clear center portion and an attenuating peripheral portion. The peripheral portion attenuates off-axis images through any radial line extending from a center of the filter or lens to a circumference edge of the filter or lens. The attenuation is for passing on-axis images with high signal to noise ratios, for attenuating off-axis images, and for attenuating but not completely blocking the off-axis images. The telescope with such a filter or lens is well suited for improved star tracking systems, and well suited for reducing off-axis glare in handheld optical apparatus such as binoculars, telescopes, cameras, and eyeglasses.
Keywords: telescope, star tracker
International Class: G02B23/12