Correct chromatic aberration; SV231 telescope filter prevents unwanted color banding in the blue range; minimizes blue wavelengths in out-of-focus areas OD 4; the higher the filter cut-off depth; the smaller the noise and the higher the imaging contrast Full thread design; .5x0.6 specification; male thread; strong and ; supports different types of filters for superimposed use AR anti-reflection coating design; transmittance exceeds 95%; improves the contrast and clarity of fast achromatic telescopes; ensures image quality and brightness; obtains more observable light Good performance coating; telescope color correction filter has plasma-enhanced dielectric coatings result in hard; scratch- and waterproof filters Specification:2inch Color: As Shown Material: Glass Package Contents: 1 * Telescope Filter Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.