The Plössl is an eyepiece usually consisting of two sets of doublets, designed by Georg Simon Plössl in 1860. Since the two doublets can be identical this design is sometimes called a symmetrical eyepiece. The compound Plössl lens provides a large 50° or more apparent field of view, along with relatively large FOV. This makes this eyepiece ideal for a variety of observational purposes including deep-sky and planetary viewing.
The chief disadvantage of the Plössl optical design is short eye relief compared to an orthoscopic since the Plössl eye relief is restricted to about 70–80% of focal length. The short eye relief is more critical in short focal lengths below about 10 mm, when viewing can become uncomfortable especially for people wearing glasses.
For a longer eye relief we reccomend considering Long Eye Relief Eyepieces.