Zeiss Vario 20-75X Zoom Eyepiece - Review - 17 Oct 2013

I received a copy of the new Vario D 15-56x/20-75x Eyepiece in the mail today from Zeiss Sports Optics. This eyepiece is new and has been designed specifically for the new and top-of-the line Victory Diascope 65T*Fl and 85T*Fl Spotting Scopes. They were gracious enough to let me test drive the eyepiece so that I could review a new digiscoping adaptor that they are about to market (more on that in a bit). This eyepiece has been out a while now, and others have had the opportunity to use it. Much of what has been discussed regarding this new ocular I was now able to address for myself.

First off, this eyepiece is larger than the previous Vario D 15-45x/20-60x Eyepiece that I currently use with my Diascope 85T*Fl (older model purchased 2003).  The new 20-75X eyepiece measures 118 mm compared to 99 mm for the 20-60X eyepiece.  It weighs 490 g relative to 330 g for the former, and its diameter (59 mm) is also a bit larger than the former (56 mm).  While the eyepiece works just fine on the older Diascopes it does not lock when attached, so its easy to accidentally unscrew it, especially when the zoom ring is new and a bit stiff.  Hopefully the zoom ring will loosen with time, but until then I have to use two hands; one to hold the collar of the eyepiece while zooming with the other.  The rubber eyecup offers nice eye relief for eyeglass wearers, and completely screws off after about 20 turns  in the counterclockwise direction.  With a twist to the right it locks down cleanly agains the lens collar.

My first impression of the eyepiece was a resounding positive.  Its bright, sharp, and offers 15X more magnification range than its predecessor.  Chromatic aberration (CA) is always a concern with me, so the first thing I did was focus on the neighbor's white awning against the blue sky.  I noticed an almost imperceptible yellowish cast to the lens, one that others have commented about.  Otherwise, no CA!  Interestingly enough, when I put my older 20-60X zoom eyepiece back on the scope, it showed NO perceptible CA.  I would later learn through a friend that a slight yellow CA is inherent in the design of the eyepiece and is almost imperceptible when viewing under normal everyday viewing conditions.  The yellow CA, unfortunately, is more noticeable in digiscoped images, which I'll address shortly.

As I've mentioned earlier with my review of the 20-60X zoom eyepiece, there is noticeable vignetting when zooming the lens between 30 - 50X magnification.  Because the internal lens elements are moving there is a distinct shadowing and narrowing of field-of-view (FOV) that makes this lens almost useless for digiscoping other than at 20X or 60X magnification settings.  On the new 20-75X zoom the vignetting between 30 - 60X is barely noticeable.  Much improvement!  As I'll write later, its possible to digiscope at every magnification range on the new zoom eyepiece if the adjoining lens is >20 mm focal length.

I then checked for edge-to-edge sharpness on the lens.  Its actually significantly improved, as well.  On the 20-60X eyepiece there is softening of detail along the outer 20% of the FOV. The new eyepiece is sharp over 95% of the FOV with only the extreme edges showing softness!

So if it weren't for the fact that the lens does not lock down on my older Diascope 85T*Fl I would find this lens a unanimous must-have for everyday viewing and digiscoping. It is available at most online optics / retail stores for $779.00.

Thank you, Zeiss Sport Optics, and Stephen Ingraham for the opportunity to test out this wonderful piece of glass!