An eyepiece filter can bring out detail in an object, assist with astrophotography, help reduce the effects of light pollution. The type of filter to used depends on what you are observing.
Types of Filters for Astronomical Viewing
Moon Filter
The moon is a beautiful sight even in a small telescope, however the moon is very bright and using a moon filter can save your night vision. A moon filter can also bring out contrast making maintains and craters sharper. Moon filters reduce irradiation, which is the distortion at the boundary between light and dark areas, such as along the lunar terminator. more...
Broadband Light Pollution Filter
A light pollution filter is a filter that is designed to eliminate the wavelengths os light that are common to man made mercury vapor, sodium and other lights. In doing so the also diminish the light from stars and and star clusters. The light from some nebulae are at a different wavelength and therefore are able to pass through the filter. Therefore these filters are best used when looking at these nebulae. Of the filters you can use to enhance nebulae this is the least effective. more...
CLS (City Light Suppression)
CLS telescope eyepiece filters are designed to reduce the effects of light pollution, making them ideal for urban or suburban stargazing. These filters work by blocking common artificial light wavelengths, such as mercury and sodium vapor emissions, while allowing the transmission of key wavelengths from astronomical objects like nebulae, star clusters, and galaxies. This results in enhanced contrast and visibility, enabling clearer observations of deep-sky objects even under light-polluted skies. However, CLS filters can reduce the brightness of some stars and are not recommended for planetary observation. more...
UHC
UHC (Ultra High Contrast) telescope eyepiece filters are specialized astronomical accessories designed to enhance the visibility of deep-sky objects such as nebulae. They work by selectively blocking certain wavelengths of light, primarily artificial and natural skyglow, while allowing the key emission lines from nebulae (Oxygen-III and Hydrogen-beta) to pass through. This results in higher contrast and better detail, making them ideal for viewing emission and planetary nebulae under both light-polluted and dark-sky conditions. However, UHC filters are less effective on galaxies and star clusters, which do not emit light in the targeted wavelengths. more...
Oxygen III
Oxygen III (OIII) telescope eyepiece filters are specialized filters used by amateur astronomers to enhance the visibility of certain deep-sky objects, particularly planetary nebulae and supernova remnants. They work by isolating the specific wavelengths emitted by doubly ionized oxygen (around 496 and 501 nm), which are prominent in these objects. By blocking other wavelengths, OIII filters increase contrast and detail, making faint structures more pronounced against the background sky. They are especially effective in light-polluted areas or under bright moonlight, helping to bring out nebular features that would otherwise be difficult to observe. more...
Hydrogen-Beta
The H-beta eyepiece filter enhances only a few emission such as the California and IC 434 making the horsehead easier to see. It will also enhance some very faint emission nebula.
This is our list of telescope eyepiece filters. Eyepiece filters can bring out detail in an object, assist with astrophotography, help reduce the effects of light pollution. The type of filter to used depends on what you are observing. more...