Svbony SV171 Zoom Eyepiece 1.25'' 8mm-24mm for Telescope

Zoom eyepieces made today are so good that I'm inclined to say that a zoom and a Barlow are all you really need. Sure, if you're in the league of exceptional ($$$) amateurs doing serious observing, that won't be true, but for hobby astronomers on a budget, I think a case can be made. First impression of this zoom eyepiece, out of the box: It's huge! With seven big pieces of glass in four groups, the SV171 is a 'serious piece of kit’. What that gets you, though, is very good optics with very good eye relief at a modest price. To be clear, this eyepiece is not suitable for small telescopes because of its size and weight (the Svbony 7-21mm zoom is what you need), but if you have a sturdy astrophotography mount it'll handle it fine. It weighs less than most cameras, after all. I went looking for optical problems but didn't find much. It's parfocal from end to end, and the eye relief is comfortable (spec says 19.5 to 16mm). I found only slight astigmatism (predictably a bit more on my ƒ/4 newt than my ƒ/10 refractor) but it wasn't enough to detect in either scope while observing the moon. Brightness, contrast, and color fringing are comparable and perhaps a little better than my Meade Series 4000 fixed focal length oculars. Using a building with lots of windows and railings about a mile away I didn't see any evidence of distortion, and when I panned across Jupiter with it at the edge of the field the planet didn't show any elongation. Two minor complaints: the twist zoom is ra

The field of view is narrow if you're used to wider field single focal length eyepieces, but it's no problem to get used to. The construction is really good quality, and the quality is really great. I only found the view to be a little soft at either end of the zoom range, but otherwise really sharp. This eyepiece is heavy and big. When it's fully in the focuser, it can interfere with the thumb screw. The solution is easy, just use a smaller-radius thumb screw, or pull the eyepiece out slightly.