More on Celestron's Filters...
Following, you'll find descriptions of the Celestron eyepiece filters included with the Viewing Accessories Kit (Cat. No. NC-8500)
Eyepiece filters are 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.
Celestron's filters are made of high quality, solid plane parallel glass with excellent homogeneity. They're anti-reflection coated to prevent glaring and ghosting. All eyepiece filters are threaded to fit Celestron's, and most other manufacturer's, 11Ú4" eyepieces, and offer a full 26mm clear aperture.
Celestron filters are mounted in black anodized aluminum cells with the Kodak Wratten Series Number individually engraved. The cells of each filter are double-threaded, so they can be stacked (piggybacked) in various combinations. This allows you to create different color combinations and transmission characteristics, or to have the same color characteristic, but with a lower transmission. When stacking color filters, the effective transmission of the combination you create is equal to the product of the spectral transmission of each of the filters used.
The effectiveness of the filters depends on several factors, including: the aperture and focal length of the telescope, the magnification being used, and seeing conditions. Filters are a simple accessory that offer an astounding variety of enhancements to aid viewing.
#12 Deep Yellow
Moon - Enhance lunar features. Jupiter - Penetrate and darken atmospheric currents containing low-hue blue tones. Enhance orange and red features of the belts and zones. Useful for studies of the polar regions. Mars - Reduce light from the blue and green areas which darken the maria, oases and canal markings, while lightening the orange-hued desert regions. Also sharpen the boundaries of yellow dust clouds. Neptune - Improve detail in larger telescopes (11" and larger apertures). Saturn - Penetrate and darken atmospheric currents containing low-hue blue tones. Enhance orange and red features of the belts and zones. Uranus - Improve detail in larger telescopes (11" and larger apertures). Venus - Reveal low-contrast surface features. Comets - Enhance definition in comet tails.
Moon - Greatly enhances lunar features. Jupiter - Improves appearance and detail revealed in structure of Jovian belts. Enhances viewing of festoons and polar regions. Mars - Reduces light from the blue and green areas which darken the maria, oases and canal markings, while lightening the orange-hued desert regions. Also sharpens the boundaries of yellow dust clouds. Mercury - Reduces the brightness of blue sky during daylight observing, to reveal surface features. Saturn - Improves structure of the Saturnian bands and highlights blue polar regions. Venus - Use during daylight observing to reduce brightness of blue sky. Comets - Enhances definition of comet dust tails and heads in larger telescopes (11" and greater aperture). Solar - When using a Celestron Mylar Solar Filter, adding this orange filter will give true color rendition.
Moon - Improves lunar features. Jupiter - Useful for studying bluer clouds. Mars - Ideal for observation of the polar ice caps and features on the Martian surface. Sharpens the boundaries of yellow dust clouds. Mercury - Improves observation at twilight, when the planet is near the horizon. During daylight, it reduces the brightness of the blue sky to enhance surface features. Saturn - Useful for studying bluer clouds. Venus - Use during daylight observing to reduce brightness of blue sky. Occasionally deformations of the terminator are visible.
#80A Light Blue
Moon - Enhance lunar detail. Jupiter - Enhance the boundaries between the reddish belts and adjacent bright zones. Useful for viewing the Great Red Spot. Mars - Very useful during the violet clearing. Helpful in studying surface features and polar caps. Mercury - Improve observation of dusky surface markings at twilight, when the planet is near the horizon. Saturn - Enhance low-contrast features between the belts and zones. Venus - Useful for increased contrast of dark shadings in upper Venusian clouds. Comets - Bring out the best definition in comet gas tails.
#56 Light Green
Moon - Enhances lunar features. Jupiter - Increases visibility of the Great Red Spot. Useful for observing the low-contrast hues of blue and red that exist in the Jovian atmosphere. Mars - Excellent for increased contrast of Martian polar caps, low clouds and yellowish dust storms. Venus - Useful for Venusian cloud pattern studies. Reduces brightness of blue sky during daylight observing.
All observing information for this filter is the same as that given for the #56 Green filter, with the exception of the following: Saturn - Enhances white features in the Saturnian atmosphere. Comets - Useful for observing brighter comets.
The above information is edited from Celestron web site at