More Information  · Images of Some Features

#23A Light Red
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. 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

#38A Dark Blue
Recommended applications for this filter:
Moon – Somewhat useful for improving contrast between lunar features in scopes 8" and larger. Mercury – May improve observations of rarely visible dusky surface features at twilight, when the planet is near the horizon. Venus – Increases contrast of occasional faint dark shadings in upper Venusian clouds. Mars – Useful for enhancing the visibility of surface features and localized dust storms, clouds, and ice fogs with 8” or larger scopes, particularly during the still-unexplained phenomenon of violet clearing (when the Martian atmosphere – normally a bright, featureless disc in violet light due to the scattering of short wavelengths of light by the thin atmosphere – becomes transparent through a violet or blue filter, revealing large dark surface features). Jupiter – Primarily used for enhancing the boundaries between the reddish belts and adjacent bright zones in the upper atmosphere. Helpful in defining the Great Red Spot and festoons in the belts. Saturn – Enhances low-contrast features between the belts and zones in the planetary disc. Comets – Brings out the best definition in comet gas tails. Useful with 10" and larger scopes for observing orange Sodium D lines in gas tails when combined with #21 filter.
17% transmission

#58 Dark Green
Recommended applications for this filter:
Moon – Excellent for enhancing the contrast of lunar features in scopes 8" and larger. Venus – Increases contrast of occasionally-visible Venusian cloud patterns. Reduces the brightness of the terrestrial sky during daylight observing of Venus (an excellent time to observe this planet, as the high contrast of Venus against the dark night sky often makes for uncomfortable and unsatisfactory observing, while during the day the contrast range is not nearly as great, irradiation within your eye is reduced, and subtle Venusian features are sometimes more visible). Mars – Excellent for increasing contrast of Martian polar caps and surface frosts with scopes 8” and larger. Jupiter – Increases the visibility of the Great Red Spot (which is more like a Faint Red Spot at the present time) with scopes 8” and larger. Useful for observing the low-contrast hues of red and blue visible in the Jovian atmosphere. Enhances white features in the planetary atmosphere. Saturn – Enhances white cloud belts and polar regions. Comets – Useful for observing brighter comets with scopes 8” and larger.
24% transmission

#ND-3 50% transmission neutral density filter
This filter reduces irradiation, glare, and brightness in lunar and planetary observing with small telescopes by allowing only 50% of the light collected by the telescope to reach your eye. Since the light is transmitted through the filter uniformly over the entire spectrum, it is excellent for planetary observing, as the bright planetary discs are dimmed to more comfortable observing levels without altering the colors. In addition, the filter can be piggybacked with color filters to provide both glare reduction and contrast enhancement. The filter also helps split binary stars of greatly differing magnitudes by reducing the glare and diffraction around the brighter star of the pair. This filter works best with telescopes 3.5” in aperture and smaller, or with 3.5" to 6" scopes when piggybacked with color filters.
50% transmission.