Astronomical Eyepiece and Solar Filters
Astronomical filters can enhance the appearance of the moon, planets, and nebulae. The moon and in some cases planets are too bright when viewed through a telescope. Lunar or neutral density filters reduce this brightness, making it easier to discern fine details. In other cases one color dominates the image and more detail can be seen if this color is partially filtered. Nebulae benefit from narrow bandpass filters that selectively pass very specific wavelengths of light being emitted by ionized hydrogen and oxygen. Solar filters are absolutely essential for safely observing the sun.
Nebular filters are designed for observing emission nebulae, dramatically increasing both the contrast and detail that is visible.
Lunar and planetary filters enhance the view by reducing glare or subduing a predominant color, allowing more subtle details to become visible.
Many astronomical filters are designed for visual observing, but some are specifically designed to be used exclusively for imaging applications using CCD or Digital SLR cameras.
Solar filters permit the safe observation of the sun with a telescope. White light filters are useful for observing sunspots. Hydrogen Alpha filters reveal details on both the surface, and in the corona.