1.The 7nm dual band filter is designed to reduce the effect of light pollution; enhance the contrast and bring out the detailed information when imaging emission nebulae 2.you can enjoy the fun of deep sky photography anytime and anywhere in urban areas; the dual-band filter helps astronomy enthusiasts to perform deep sky photography in urban areas with serious light pollution or under a full moon 3.Lower the threshold for making astronomical works; the dual-band filter makes it possible to simplify and decrease the difficulty and cumbersomeness of post-processing for users 4.Compared with traditional black-and-white deep sky photography; dual-band filter can achieve a single exposure to capture large full-color images The SV231 color correction filter is designed with full thread and standard size to compatible with different types of telescope. The filter can eliminate blue strips, restore the real image. Make your astronomy experience better. The optical density is greater than 4. Low noise and high imaging contrast. The SVBONY 2" Color Correction Filter is fully threaded and designed for 2" eyepiece. Compatiable with SV503,you can perform astronomical observations without color difference. The effective working wavelength range of the filter is 300-1200/NM. High transmittance means high level of transparency, allows a significant amount of light or energy to transmit through it. Compatiable with SV48P,you can perform astronomical observations without color difference. The NIR is fully blocked up to 1150nm. Details on planets are shown much clearer when using CCD/CMOS-cameras. Planeoptically polished; 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 afocal projection with digital cameras. Excellent optical performance and color expression add color to your deep sky photography.