| These proprietary wide field designs use five to seven lenses to achieve a wide 65 degree apparent field of view (except the 28mm, which has a still-wide 55 degree field). With the exception of the zoom, they all have a very long 20mm eye relief that give fully unvignetted views for those who must wear eyeglasses while observing. Rotating each eyepiece’s rubber eyecup raises and lowers it to the desired height to customize the eye relief to match your eyesight. They are designed to run the full gamut of magnifications, from low power to very high power, and to be used with all telescope types. They are threaded for standard light pollution and color filters. All are fully multicoated with Pentax’s proprietary Super Multi-Coatings (SMC) and have blackened lens edges for better contrast. All use ED (extra low dispersion glass) elements to minimize chromatic aberrations and astigmatism. They are usable for all types of observing, with all telescope types, and are corrected for use with focal ratios down to f/4. They have good contrast and excellent center to edge sharpness, with very little ghosting. These are quite good wide field eyepieces at prices that are quite reasonable for the performance you enjoy. |