Now even casual telescope users can enjoy the benefits of zoom eyepiece technology. A simple twist of the barrel of the affordable E-Series Zoom eyepiece changes the focal length from 21mm to 7mm, or to any focal length in between. That makes it ideal for locating an object at low magnification, then quickly zooming in to higher magnification for closer inspection, all without changing eyepieces! Actual magnification range will depend on the focal length of your telescope, but as an example: in an Orion SkyQuest 8" Dobsonian reflector with a 1200mm focal length, this eyepiece provides a continuous magnification range of 57x-171x. And the E-Series Zoom works equally well for astronomical or terrestrial viewing in smaller refractor or Cassegrain design telescopes. This 6 element telescope eyepiece boasts fully multi-coated optics and exceptionally long eye relief ranging from 18mm (at 21mm) to 16.3mm (at 7mm). The apparent field of view angle ranges from 40-deg (at 21mm) to 57-deg (at 7mm). The 1.25" barrel is threaded for standard eyepiece filters. A very nice value in a quality zoom eyepiece!

The 1.25" barrel is threaded for use with like-sized Orion eyepiece filters. Exceptionally long 18mm-16.3mm eye relief range allows eyeglass wearers to enjoy the entire field of view without needing to remove their glasses. The eyepiece consists of six lens elements, which are fully multi-coated with anti-reflection coatings for bright and clear views, rich in contrast. A simple twist of the zoom eyepiece housing changes the focal length from 21mm to 7mm, providing a variety of viewing magnification powers. The Orion E-Series Zoom eyepiece allows you to change magnification power without swapping out eyepieces.

Focal Length Description: 21 millimeters. Lens Coating Description: Fully Multi-Coated. Finderscope: Reflex. Focus Type: Manual Focus. Telescope Mount Description: Altazimuth Mount. Objective Lens Diameter: 21 Millimeters. Eye Piece Lens Description: Plossl. Brand: Orion. Manufacturer: Orion. Date First Available: November 1, 2003. Best Sellers Rank: #77 in Telescope Eyepieces. Customer Reviews: 4.7 out of 5 stars 125 ratings 4.7 out of 5 stars. : B084RDVHFQ. Item Weight: 8.7 ounces. Package Dimensions: 4.41 x 2.99 x 2.76 inches.