From the ManufacturerFour-element 12.5 mm focal length 1.25" Plossl telescope eyepiece with an illuminated double crossline reticle. Excellent for accurate polar alignment, GoTo system alignment, IntelliScope system alignment, and acquiring and centering of guide stars for guided astrophotography pursuits. Fully multi-coated lenses provide bright views with a 40 Degree apparent field of view. LED-illuminated double crossline reticle has adjustable focus and brightness. Illuminator requires three GP-189 batteries (included)