Astro-Tech #12 Medium Yellow 1.25" Color Filter

This #12 medium yellow Astro-Tech 1.25" eyepiece filter is helpful in improving lunar and Martian contrast in telescopes 4" to 8" in aperture, particularly if combined with a polarizing or neutral density filter when used with the larger apertures.  Similar in performance to the #8 light yellow filter, but more pronounced effect. Its transmission is somewhat better suited to scopes in the 4" to 8" aperture range, while the #8 filter's transmission is better suited to apertures 3.5" and below.

Recommended applications for this filter:

Moon - Improves contrast between lunar features of varying brilliance in scopes 4" and larger, especially when combined with a polarizer or neutral density filter with scopes in the 6" to 8" aperture range. 

Venus - Occasionally helpful in revealing low-contrast banding in the thick Venusian cloud cover.

Mars - Increases the contrast of polar caps, frost areas, low clouds, and dust storms against the ochre deserts. Also sharpens the boundaries of yellow dust clouds.

Jupiter - Somewhat useful for darkening atmospheric currents containing low-hue blue tones and enhancing detail in small orange-red zonal features in the belts. Useful for studies of the polar regions.

Saturn - Somewhat useful for darkening atmospheric currents containing low-hue blue tones and enhancing detail in orange-red zonal features in the belts. Improves the visibility of Cassini's Division in the rings.

Neptune and Uranus - Somewhat useful for enhancing very subtle dusky features in scopes 10" and larger.

Comets - Brings out highlights in yellowish comet dust tails and improves the contrast of comet heads.

 74% transmission