The SVBONY MK90 features a convex meniscus lens instead of a traditional Schmidt corrector plate, enhancing contrast and eliminating the need for periodic collimation, instant readiness for stargazing; each astronomical photography telescope undergoes precise optical axis alignment before leaving the factory; 3 screws for fixation; 3 pairs of calibration screws; enjoy immediately easy to use. SV128 polarizing filter will fit all standard sized 2" eyepieces and accessories, SV128 polarizing filter consists of two polarizing filters; One can be rotated in its cell to adjust the brightness, progressively dim the view when observing a bright object; Such as the moon or certain planets.