* Astronomy

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+ degree 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.
Source 

Expand (31kb, 1024 x 701)

1.25" 5mm BST Explorer Dual ED eyepiece

The eyepiece uses two separate ED (Extra-low Dispersion) glass elements of different glass types in its optical system to provide exceptional colour fidelity (with astonishingly low levels of chromatic aberration) so that the true colour differences between binary star pairs and planetary surface details are easily visible. It has a  60° field of view which is very flat and it is particularly recommended with telescopes with a f/5, or greater, focal ratio. It is uniformly sharp edge-to-edge, with markedly low astigmatism. Barrel distortion is essentially non-existent, eliminating the annoying "goldfish bowl" effect of distortion of the image which is often seen in some eyepieces when panning across a star field.
Each air-to-glass surface in the eyepiece is fully multicoated for high light transmission and exceptional contrast.  This high contrast makes it a good choice for splitting close binary stars, for examining low contrast lunar and planetary detail, and for finding small and faint planetary nebulae against a truly dark sky background.  The lens edges are blackened to eliminate internal reflections and further improve contrast.
As you would expect, the chrome barrel is threaded for standard 1.25" filters and has a capture ring to help reduce the chances of accidentally dropping the eyepiece out of the focuser.  Explorer eyepieces are parfocal, minimising the amount of refocusing needed when changing eyepieces within the series.
The eyepiece is set in a heavy rubber cladding which is grooved for easy grip.  It has a soft rubber twist up eyecup which will make it unbelievably convenient to those of us who wear spectacles. The colour coded body rings and clear lettering print will help you find the right one in the dark.
The eye lens is large in diameter and with 13mm eye relief this makes it very comfortable and easy to look through.  It weighs 7.4 ounces.

Coating: FMC fully multi-coating
Focal Length: 5, 8, 12 15, 18 &  25mm
Lens Structure: 6 elements 4 groups
Price: £41.00

See more

Sky-Watcher 'SP-Series' Super Plossl Eyepieces

These standard 1.25 inch/31.7mm eyepieces set high performance standards for modern telescope oculars. The proven 4-element Plossl designs display edge-to-edge pinpoint imaging across their panoramic 52º fields. Utilisation of top quality optical glass, superior multi-layer coatings and edge-blackened elements deliver superb high contrast images.
Read more

£19.99