What makes an eyepiece a planetary EP?
The typical eyepiece today is designed for wide-field views of deep space objects (DSO). They offer a portal to the sky, where the DSO of interest is nicely framed. To achieve these nice, wide field of views, design choices have to be made, such as using a large number of elements and groupings of elements. These design choices sometimes result in lateral color. Lateral color is an abberation where different colors intercept the focal plane at different points and can be seen when viewing bright objects off-axis. When observing dim DSO, lateral color in the typical eyepiece is rarely seen. Also, these design choices sometimes result in light scatter, seen as a halo or glow around bright objects. Again, light scatter is rarely seen when observing dim DSO. If there is a bright star near the edge of the field, then lateral color and light scatter might be seen when observing dim DSOs. But, the lateral color and light scatter would be associated with the bright star, not the DSO. The desig
