Astromania Zoom Eyepiece for Telescope, 7-21mm Zoom Lens Variable Power & Multi-Coated Design for Planetary & Deep Space Observation Compatible with Telescope That Accepts Telescope Eyepiece 1.25 Inch

A twist of the zoom eyepiece housing changes focal length from 21 mm to 7 mm providing a variety of viewing magnification powers; excellent contrast and sharpness making the zoom also of interest for planetary observing Exceptionally long 16 mm to 33 mm eye relief range allows eyeglass wearers to enjoy the entire view while still wearing their corrective lenses without vignetting; the Zoom eyepiece lets you change magnification power without physically changing eyepieces Apparent field of view is 30 degree at 21 mm and 43 degree at 7 mm; rubber traction ring ensures a good grip; the 1.25 inch barrel is threaded for filters; actual magnification range will depend on the focal length of your telescope Eyepiece consists of four elements which are coated with anti-reflection coatings for clear and high contrast views; the large eye lens coupled with the long eye relief means the Zoom provides particularly good viewing comfort; the eyecup can folded down Comfortable viewing at every focal length setting superior to most fixed focal length eyepieces; especially at the shorter focal length settings; precise and stepless adjustment from 7mm to 21mm; a nice value in a quality zoom eyepiece