SV503 70mm telescope is ideal for observing galaxies, nebulae and star clusters, delivering crisp and bright images. It with built-in field flattener and Extra-Low Dispersion Glass, which can virtually eliminate the field curvature and chromatic aberration,providing true colors.SV135 fully multi-coated zoom plossl eyepiece zooms to any focal length between 7 mm and 21 mm - pick the better magnification for your subject. As a beginner; SV135 zoom eyepiece is good for starter astronomer!Reducing the amount of light entering the eyepiece increases the contrast between the moon and the star, allowing you to see more details about the moon and the stars. 26mm is the clear aperture diameter. Adjust the amount of light transmission from 1% to 40% by rotating the filter housing.