Astro-Tech #23A Light Red 1.25" Color Filter

This #23A light red Astro-Tech 1.25" eyepiece filter is useful when observing Mercury and Venus during the day and at twilight and when observing Mars, Jupiter, and Saturn with telescopes 4" in aperture and larger.

Recommended applications for this filter:

Moon - Somewhat useful for improving contrast between lunar features in scopes 8" and larger.

Mercury - Improves observations at twilight, when the planet is near the horizon. Reduces brightness of terrestrial sky to enhance daylight observing.

Venus - Reduces brightness of terrestrial sky in daylight observing, allowing occasional terminator deformations to be seen.

Mars - Filters out scattered blue light in the Martian atmosphere to Increase the contrast and definition of polar caps, frost areas, low clouds, and dust storms against the ochre deserts, particularly when Mars is close to Earth's horizon, as the red light it passes is the least refracted by air currents in our atmosphere. Reduces light from blue and green areas which darkens the maria, oases, and canal markings, while lightening the orange-hued desert regions. Sharpens the boundaries of yellow dust clouds.

Jupiter - Brings out structure in the belts and enhances festoons and polar regions.

Saturn - Useful on Saturn for studying the bluer cloud bands and polar regions.

Comets - Enhances the definition of comet dust tails in 10" and larger scopes.

25% transmission