Test Result
Art. –Nr. SKY-Zoom-7-21
Skywatcher Zoom Eyepiece 7 to 21mm
Sharpness at 21mm:
Fine over the complete field of view.
x-axis: distance from optical
axis in °, y-axis: resolution in arc minutes
Sharpness at 7mm:
Good in the center, but really blurred towards the edges. Of course a
field curvature makes it necessary to focus the center or the edge area.
x-axis: distance from optical
axis in °, y-axis: resolution in arc minutes
Apparent Field of View:
The apparent field of view is approx. 26° at 21mm and up to 39° at 7mm.
Contrast:
At 21mm: very good. Down to 7mm contrast gets noticeably worse.
Aberration:
Nearly free of distortion over the whole zoom range. At low focal length
chromatic errors in the edge area occur.
Eye Relief:
Comfortable.
Mechanical Quality:
Nice quality with foldable rubber eye cup and grip coated body. The zoom
mechanics is very good, perfectly balanced between tight and loose. There are
no “click-ins” for defined focal lengths.
Summary:
Mechanically recommendable, but with optical drawbacks.