I'm not to astronomy, i purchased this 2.5* barlow lens with the StellaLyra 8" dobsonian to give a few more options with the eyepieces that came with the scope. The lens itself is great quality,. Importantly the quality of the view through it is great to my eye. I don't perceive a lot of reduction in light level when compared to an eyepiece without this lens and the magnification with this and a 15mm eyepiece on the 1200mm focal length scope, seems to me to be about right for viewing Jupiter and Saturn with a reasonable degree of detail visible.