This eyepiece is very good and very cheap. Also for the Bino observation very interesting, because the focal lengths can be set very fine and are therefore easy to bring congruent.
 
The latest generation of Sebens 31.7mm (1.25 ") Super Zoom Plössl eyepieces in the highest optical quality and finish. The stepless adjustability of the focal length from 8mm to 24mm offers the user the possibility to quickly and easily achieve different magnifications with his telescope or spotting scope. The Seben Super Zoom Plössl eyepiece 8-24mm replaces some of the Plössl eyepieces.

With the new Seben Super-Zoom Plössl eyepiece 8-24mm, celestial, animal and nature observation as well as planetary observation will not only be more convenient, easier and more fun, but you will also save real money. Instead of buying multiple eyepieces, all you need is a Seben Super Zoom Plössl Eyepiece 8-24mm!

Technical details:

• Stepless zoom from 8mm to 24mm focal length
• 31.7mm (1.25 ") connector
• T2 thread under the eyecup
• Viewing angle: 60 ° at 8mm focal length - 40 ° at 24mm focal length
• Eye distance consistently at about 20mm
• Optimizing the image quality of your telescopes or spotting scope
• High translucence
• High-Resolution
• Multi-tempered 6-lens system
• Filter screw thread for the use of contrast filters
• Stable transport and dust container included
• Eyecups for eyeglass wearers

 
You can calculate the magnification by dividing the focal length of your telescope by the focal length of the eyepiece; In this case, it depends on which focal length you have chosen in your Seben Super Zoom Plössl eyepiece, because its infinitely variable zoom of 8mm to 24mm focal length allows you to adjust numerous magnifications!