SV48P 102mm f6.5 Astronomical Telescope has outstanding optics, high-quality mechanical components. Fitted with achromatic glass for good edge-to-edge viewing, fully multi green coated lens maximize light transmission eliminating false color. The 2.5inch Double speed focuser, for smooth operation, great feel and precise adjustability. This is a good telescope provides for astrophotography visual observers or nature watchers. The 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. It can effectively block light damage and reduce noise. Standard 1.25-inch astronomical filter size specifications: meet the needs of telescopes of different apertures and cameras with different target surfaces. Adopting AR anti-reflection coating, the pass rate is more than 95%, ensuring image quality and brightness. P This way, details on planets are shown much clearer when using CCD or CMOS-cameras, too. The SV231 color correction filter can be used well before the focal point of the optical system, without any loss of sharpness, as a single filter in front of a binocular for a focal projection with digital cameras. Compatiable with SV503 or SV48P, you can perform astronomical observations without color difference. High transmittance means high level of transparency, allows a significant amount of light or energy to transmit through it.