Astronomical filters enhance the appearance of specific targets.
Lunar and planetary filters reduce brightness and glare, and reveal subtle detail that is lost when one color dominates the object.
Nebular filters serve to increase the contrast and detail visible in emission nebulae.
White light filters allow one to observe sun spots or any dark object passing in front of the sun.
Hydrogen-alpha filters take solar observing to an entirely new level by revealing prominences around the solar limb and texture on the solar disk itself.
Calcium K filters are used to study an emission line from a layer of the chromosphere that is slightly lower and cooler than the layer viewed in Hydrogen-alpha.
Helium D3 and Sodium D filters are used by researchers and professional solar observatories to study different layers of the chromosphere.