Colour Magic C1 Duo-band filter (Hα+OIII) has a high transmittance of over 90% at its center wavelength (500.7nm and 656.6nm). It can effectively improve the quality of the image by making the sky background of the image darker while maximizing the contrast throughout the image, enhancing the contrast of your pictures, and making it easier to display the details of the stars. In areas with very serious light pollution, this filter can also selectively filter light pollution and cluttered signals through the emission lights of the nebula to achieve the ideal shooting effect.