The Prostar 68° range of 1.25” eyepieces is an economical way to get a super wide angle Apparent Field of View (AFOV).
As with contemporary eyepiece designs, the Prostar 68° range is not a particular design, but a set of eyepieces that gives a super wide 68° AFOV, with long eye relief and large eye lens (the lens you look into).
These 68° eyepieces offer fully multi-coated lenses with blackened edges to reduce ghosting/internal reflections and improve contrast.
The Prostar 68° range of 1.25” eyepieces are best suited to refractors, Cassegrains and to slower f/ratio Newtonians.
Note that achromatic refractors show achromatic aberration, and this will be more significant as the eyepiece focal length becomes shorter. To help overcome this blue flaring, a Yellow #12 filter or Baader Fringe Killer filter can be used to reduce this effect.