Click Here to see our selection of astronomical filters.

The Deep-Sky Hydrogen-Beta , Oxygen III , and Ultra High Contrast Filters are the result of 20 years of steady design improvements, and continue to deliver the highest performance of all anti-light pollution filters obtainable today. The following information recommends which filter to use on which celestial objects, and explains how filter transmissions differ.

WRATTEN COLOUR FILTERS

#8 Light Yellow (83% transmission) Used to enhance detail in red and orange features in the belts of Jupiter. Is useful for increasing mare contrast on Mars and improving disc resolution of Uranus and Neptune with larger telescopes. Can be used to enhance lunar detail also.

#11 Yellow-Green (78% transmission) Excellent for bringing out surface details on Jupiter.
Darkens the mare regions on Mars.

#12 Yellow (74% transmission) Enhances red and orange features of Jupiter and Saturn, while blocking blue and green wavelengths. It also lightens red and orange features on Mars, while reducing, the transmission of blue and green areas. This filter increases the contrast between the two. Also enhances the blue clouds in the Martian atmosphere. Can also be used to increase contrast in lunar features with telescopes of 150mm aperture and larger.

#15 Deep Yellow (67% transmission) Used to bring out Martian surface features, and the polar ice caps. It can also be used to enhance the orange and red features, bands and festoons, on Jupiter and Saturn, and low-contrast cloud details on Venus.

#21 Orange (46% transmission) Reduces transmission of blue and green wavelengths, thus increasing the contrast between these areas and red or yellow or orange areas. Works very well with Mars. Sharpens the boundaries between these areas on the planet's surface and can sharpen the contrast in the belts of Jupiter also enhancing the Great Red Spot. Has slightly more contrast than the Wratten #15.

#23A Light Red (25% transmission) A popular filter for use when observing Mars, Jupiter, and Saturn. Due to the lower light transmission of this filter, it is best used with telescopes larger than 130mm aperture. It performs many of the same functions as the #21 and the #15 but with somewhat more contrast. Can be a useful filter for daylight observations of Mercury and Venus. improving contrast between these planets and the pale blue sky.

#25 Red (14% transmission) The #25 and #25A filter strongly blocks the transmission of blue and green wavelengths which results in very sharply defined contrast between the cloud formations and the lighter hue features of Jupiter. Also quite useful for improving definition of the Martian polar ice caps and darker mare surface regions.

#38A Dark Blue (17% transmission) Very good for use on Jupiter because it strongly rejects red and orange wavelengths in the belts and in the Great Red Spot, thus increasing contrast. It works well on Martian surface phenomena, like dust storms, and increases contrast in the rings of Saturn. Most suitable for Venus given its low light transmission and readily increases contrast of subtle cloud markings.

#47 Violet (3% transmission) Strongly rejects red, yellow, and green wavelengths, making it suitable to use on the Martian polar ice caps. It is the best filter for observations of Venus due to its low light transmission and ability to enhance upper atmosphere phenomena. Also can be used for enhancing lunar detail. Presents interesting views of Jupiter and its satellites.

#56 Light Green (53% transmission) Very good for observing Martian polar ice caps and yellow tinted dust storms on the planet's surface. Also increases the contrast of the red and blue regions in Jupiter's atmosphere and cloud belts.

#58 Green (24% transmission) Strongly rejects red and blue wavelengths increasing their contrast on the lighter regions of Jupiter's cloud tops. Useful for enhancing the cloud belts and polar regions of Saturn. Great for increasing contrast in polar ice caps of Mars and does a reasonable job at improving contrast of atmospheric features on Venus.

#80A Blue (30% transmission) A magnificent all-round filter. Perhaps the best economical filter for studying planetary detail of Jupiter and Saturn. Enhances contrast of festoons and other disturbances in Jupiter's cloud belts, along with detail of the Great Red Spot. Works great with Saturn revealing terrific detail in its belts and polar features. Can be useful for lunar observations.

#82A Light Blue (73% transmission) Another outstanding performer like the #80A and works well with Jupiter, Mars, Saturn and the Moon. Its pale blue colour enhances low contrast areas and avoids significant reduction of overall light level at the same time.

ND96 Neutral Density (0.9 density, 13% transmission) The neutral density filter transmits light uniformly across the entire visible spectrum making it an excellent tool for glare reduction and studying bright localised lunar surface regions around times of full Moon. Suitable also to improve contrast when splitting difficult double stars.

SPECIAL FILTERS

Deep Sky UHC & CLS filters

Intended for viewing nebulae from light-polluted skies.
Blocks all mercury vapour and high & low pressure sodium vapour lamp light, neon lights and airglow, while transmitting the rest of the visible spectrum. The best all-around visual light pollution filter for use in urban skies.
This filter also provides high-contrast views of the Martian polar caps

Ultra High Contrast Filters

Baader and ProStar narrow band pass filter isolates the two doubly ionized oxygen lines (496 and 501nm) and the hydrogen-beta line (486nm) emitted by planetary and most emission nebulae. Provides superb views of the Orion, Lagoon, Swan and other extended nebulae. The best all-around dark-sky nebular filter available.

Oxygen III Filters

Narrow band pass filter (11nm) isolates just the two doubly ionized oxygen lines (496nm and 501nm) emitted by planetary and extremely faint nebulae.Produces near-photographic views of the Ring Neb, Dumbbell Neb and Orion Neb etc.

Hydrogen-Beta Filters

Extremely narrow bandpass filter isolating the hydrogen-beta line alone (486nm).Excellent for viewing the Horsehead, Cocoon and California Nebulae. Often the only way to view certain nebulae and are best used under clear skies with large aperture telescopes.
 

See specifications for ProStar Narrow band filters here

QUICK GUIDE TO PLANETARY FILTERS