What are the different types of eyepiece filters: Colored, Neutral Density and Polarizing?

Eyepiece filters are a gamechanger for lunar and planetary observing. They can reduce glare and light scattering, increase contrast through selective filtration, increase definition and resolution, reduce irradiation, lessen eye fatigue, and more.

Most quality eyepieces have threads in the base of the tube to accept filters. Many manufacturers use standard threading so you can mix and match the filters and eyepieces in your collection.

 

 

A filter’s effectiveness depends on several factors, including: the aperture and focal length of the telescope, its magnification, and current seeing conditions. In the sections that follow, we’ll walk you through what to expect from each filter—Yellow, Orange, Red, Blue, Green, Violet, ND and Polarizing—in different observing situations. You’ll also become familiar with the variety of ways these simple accessories can enhance your views. For each filter, we’ll provide the percentage of light transmitted, noted as T.

Yellow             Orange            Red         Blue                Green                 Violet                 Neutral Density                 Polarizing                 Oxygen III                 UHC/LPR

 

#12 Deep Yellow 74% T
#15 Deep Yellow 67% T

Use these yellow filters to —

Moon	Bring out lunar surface features.
Jupiter	Penetrate and darken atmospheric currents containing low-hue blue tones. Enhance orange and red features in the belts and zones. Study 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. Sharpen the boundaries of yellow dust clouds.
Neptune	Improve detail in telescopes with 11" apertures or larger.
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 telescopes 11" or larger in aperture.
Venus	Reveal low-contrast surface features.
Comets	Enhance definition in comet tails.

 

#8 Yellow 83% T

This filter offers the same benefits as the #12 and #15 Deep Yellow filters described above, with the following exceptions. Use the #83 Yellow filter to —

Mars	Improve the views of Martian maria by reducing scattered light from blue areas, while allowing additional green light to pass through for studying yellow dust clouds.
Comets	Bring out highlights in yellowish dust tails. Enhance the appearance of comet heads.

 

#21 Orange 46% T

Use this filter to —

Moon	Greatly enhances the appearance of lunar surface features.
Jupiter	Bring out structural details in the Jovian belts. Enhance views of festoons and 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. Sharpen the boundaries of yellow dust clouds.
Mercury	Reduce the brightness of blue sky during daylight observing and bring out detail.
Saturn	Reveal structure in the cloud bands. Highlight blue polar regions.
Venus	Reduce the brightness of blue sky during daylight observing.
Comets	Enhance definition of comet dust tails in telescopes 11" or larger in aperture).
Solar	Provide truer color rendition when combined with some solar filters.

 

#25 Red 14% T

Use this filter to —

Moon	Bring out lunar surface features.
Jupiter	Study bluer clouds.
Mars	Observe the polar ice caps and features on the Martian surface. Sharpen the boundaries of yellow dust clouds.
Mercury	Improve views at twilight when the planet is near the horizon and bring out detail. Reduce the brightness of the blue sky during daylight observing.
Saturn	Studying bluer clouds.
Venus	Reduce the brightness of the blue sky during daylight observing. Sometimes reveal deformations of the terminator during Venus' crescents and gibbous phases.

 

#23A Light Red 25% T

This filter offers the same benefits as the  #25 Red filter described above, with the following exceptions. Use the #23A Light Red filter to —

Mars	Reduce light from blue and green areas which darkens the maria, oases and canal markings, while lightening the orange-hued desert regions. Sharpen the boundaries of yellow dust clouds.
Comets	Improve definition of comet dust tails.

 

Light Blue 30% T
#82A Pale Blue 73% T
#38A Blue 17% T

Use this filter to —

Moon	Enhance lunar surface detail.
Jupiter	Enhance the boundaries between the reddish belts and adjacent bright zones. View the Great Red Spot.
Mars	Observe the planet during the phenomenon known as the blue or violet clearing, when we can see Martian features in blue or violet light for a period of several days. Study surface features and polar caps.
Mercury	Bring out dusky surface markings at twilight when the planet is near the horizon.
Saturn	Reveal low-contrast features between the belts and zones.
Venus	Increase the contrast of dark shadings in upper Venusian clouds.
Comets	Bring out the best definition in comet gas tails.

 

 

#56 Light Green 53% T

Use this filter to —

Moon	Enhances lunar surface features.
Jupiter	Increase visibility of the Great Red Spot. Bring out the low-contrast hues of blue and red that exist in the Jovian atmosphere.
Mars	Increase contrast of Martian polar caps, low clouds and yellowish dust storms.
Venus	Study Venusian cloud patterns. Reduce the brightness of blue sky during daylight observing.

 

#58 Green 24% T 

This filter offers the same benefit as the #56 Light Green filter described above, with the following exceptions. Use #58 Green filter to —

Saturn	Enhance white features in the Saturnian atmosphere.
Comets	Observe brighter comets.

 

#47 Violet 3% T

Use this filter to —

Mars	Detect high clouds and haze over the Martian polar caps.
Mercury	Detect faint features.
Saturn	Study ring structure.
Venus	Increase contrast of dark shading in upper Venusian clouds.
Comets	Observe brighter comets.

  

#96ND 50% T – Density 0.3
#96ND 25% T – Density 0.6
#96ND 13% T – Density 0.9

Use this filter to —

Moon	Reduce irradiation, glare and subject brightness without affecting the Moon's color, as light is transmitted uniformly over the entire spectrum. (Each model performs somewhat differently, depending on the brightness of the Moon).
Planets	Lower overall levels of light transmission to reduce brightness without affecting color, especially when stacked with other filters. Reduce glare and minimizes irradiation on brighter planets.
Binary (Double) Stars	Split binary stars by reducing glare and diffraction effects around the brighter star of the binary pair.

Use this filter to —

Moon	Reduce irradiation and glare. (this filter is ideal for this!)
Planets	Reduce irradiation and glare. (this filter is ideal for this!)
Binary (Double) Stars	Split binary stars by reducing glare and diffraction effects around the brighter star of the binary pair.

 

Use this filter to —

Deep Space

Isolate the two doubly-ionized oxygen lines (496 and 501nm lines) emitted by planetary and emission nebulae, providing an extreme contrast between the black sky and the faint photons of OIII light. Achieve detail views of the Veil, Ring, Dumbbell, Crescent and Orion nebulae, among other objects in rural or urban areas.

 

Use this filter to —

Moon, Planets, Binary (Double) Stars	Darken the sky background and boost contrast. Block mercury vapor, high- and low-pressure sodium vapor lights, and the unwanted natural light caused by neutral oxygen emission in our atmosphere (i.e. sky glow).
Deep Space	Darken the sky background and boost contrast in nebulae, galaxies, and star clusters. (This is the perfect filter for viewing nebula from light polluted skies, or for boosting the contrast of nebula from dark sky sites.)

 

For a quick reference of which filters work for different celestial objects, we’ve created this handy chart for easy reference. Click the image for a free, downloadable PDF version