Glossary of Technical Terms
Field of view
As of a subjective
(perceived)
field of view of 60 degrees, eyepieces may be
designated as wide angle eyepieces. However, by means of the additional 24
degrees, which this UWA eyepiece with a subjective field of view of 84 degrees
offers, one can take double the area in.
Setup
The large field of view with an enhanced observation comfort due to the bigger
longitudinal eye distance is implemented by means of an intermediate image located
in the eyepiece. This image together with small-sized pupil aberrations
(imaging
errors)
ensures a relaxed, accommodation-free
(adaptation-free)
observation.
The use of glasses with normal and abnormal dispersion paths leads to very good
and homogenous imaging properties throughout the entire field of view and strongly
suppressed lateral chromatic aberrations. Hence, this eyepiece also suits for general
use on telescopes with short focal lengths and fast apertures. Besides, the
eyepiece’s slim construction allows for binocular applications.
Anastigmatism
This eyepiece is free from astigmatism. Point-shaped objects (e.g. stars) are sharply
reflected as points throughout the entire field of view (even in the outer portions).
Unlike other eyepieces where high-resolution viewing of fine structures is possible
near the axis only, this eyepiece allows viewing up to the edge.
Dispersion
In most of the transparent materials, normal dispersion occurs in the visible range.
On these materials, the refractive index, with increasing wave length, decreases from
blue to red, whereas in case of abnormal dispersion the refractive index increases
with the wave length.
Distortion
The distortion
(optical deformation)
is a geometric imaging error that results in local
changes of the imaging scale. Basically, distortion is necessary in order to facilitate a
steady and comfortable observation.
At this eyepiece, the distortion V=17.3% for that large field of view is already little.
For further information also see:
Summary of Contents for DOCTER UWA Eyepiece
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