Filters are very common in astronomical imaging. They provide the ability to remove unwanted wavelengths of light, such as that of light pollution from street lighting, or infrared light from stars or planets when you are trying to image their normal light. Alternatively they also allow you to capture only one particular wavelength (although in practice a band rather wider than a single wavelength will be covered). Filters can be used for light polluted skies, planets, deep sky objects, galaxies, nebulae, planetary nebulae, comets, and solar prominences.
Planetary observers work endlessly to improve the definition of telescopic images of the Moon and planets. While using filters will not eliminate optical defects in the telescope they will help improve image definition even in a bad system.
New Products For May - Filters
GSO 1.25" Nebula Filter