SVBONY SV220 dual narrowband H Alpha/O III 7nm narrowband 1.25 inches filter is specially designed for astrophotography in light-polluted environments, allowing imaging under bright artificial light pollution and moonlight conditions to capture color images without using multiple filter combinations. Images are most useful with single-use color cameras; can be used for imaging emission nebulae, planetary nebulae, and supernova remnants; high transmittance and sharp cutoff can greatly enhance contrast, showing the most detailed information about deep sky objects; designed to drastically cut off sodium Artificial light interference from vapor or mercury vapor street lights and other unwanted interference; dual Band Narrow Band Filters are not suitable for visual observation and are not designed for imaging or observing the sun. Please note that SV220 is not well suited for fast telescopes, some users have reported that dual-band OSC filters paired with RASA can cause band shifts, thus clipping HA data. SV231 filter is specially used to correct chromatic aberration and color unevenness. It improves the color quality and contrast of the picture by eliminating chromatic aberration and enhancing color saturation. If you have ever been troubled by the edge chromatic aberration problem of your telescope, try this one, you may be pleasantly surprised. Standard 1.25 inch astronomical filter size specifications: meet the needs of telescopes of different apertures and cameras with different target surfaces.