The only drawbacks to the Swarovski AT 80 and AT 80HD are their size and weight. If you have been a reader of BVD for long you already know that I think the Swarovski 20-60X zoom eyepiece is simply the finest zoom, and perhaps the finest eyepiece of any kind, currently available for spotting scopes. Given that, it made sense to look at the other two Swarovski scopes that take the zoom.
Draw tube scopes are not popular in the United States. I don't really know why, what the history might be, but the fact is I have never seen one in the field. You may not even know what I am talking about. Most spotting scopes sold in the US are prismatic scopes that use porroprisms just like those in porro binoculars to erect the image (turn it right side up and right way round). That gives them the characteristic dog leg look, generally with the eyepiece offset above the objective lens. They focus internally, either with a knob on the prism housing, or with a helical collar on the barrel of the scope. A draw tube scope is a modern adaptation of the old fashioned seaman's collapsing (telescoping ) telescope, in which the sections of the barrel slide inside each other when collapsed. The only difference is that the traditional collapsing telescope used a Galilean erecting system (lenses) while most modern draw tube scopes use roof prisms. The use of prisms allows them to be considerably shorter, even when fully extended, than traditional telescoping telescopes.
The two Swarovski draw tubes are typical of the design. The fully collapsed CT75, with the 3 inch zoom eyepiece attached, still measures under 16 inches, and weighs just 2.5 pounds. The CT85, which uses two draw tubes instead of the 75's one, collapses to 13 inches with the zoom attached, and weighs 3 pounds. Fixed power eyepieces subtract about another 2 inches, and some weight. Extended, both scopes measure (again with the zoom) about 22 inches. I say about because the length varies with focus. Unlike some draw tube scopes, which simply slide in and out to focus, the Swarovskis also have a helical mechanism built in that allows you to turn the end barrel of the telescope in and out for very precise focus adjustment. The exterior of the main barrel of both scopes is heavily rubber armored (in green), and the draw tubes are finished in what appears to be very high quality black matte enamel. Both scopes have excellent built in, slide out, lens shades. The extending and collapsing motion is silky smooth, as is the helical focus. It is somewhat disconcerting, the first time you collapse the scopes, to hear and feel the bicycle pump like woosh of escaping air, but the Swarovski instructions make it clear that there are dust filters and seals in the system to keep most contaminants out of the inside. They do make a point of saying that the scopes are not, because of the necessary displacement of air, waterproof. It is possible that some condensation would form on the inside of the scope in very cold weather. In our admittedly dryer than average New Mexico climate, I had no problems with interior fogging on even the coldest days--even coming directly into a heated and more humid home.
I have to admit that, while I thought the draw tube scopes were worth a look, I did not expect to like them much. Swarovski seems to take delight in making nonsense of my prejudices. Not only do they make a zoom I can like (love), but now they show me a roof prism scope I could live with. Every roof prism scope I have tested up to this point has been disappointing. None of them have the crisp, bright, detailed image that I am used to in conventional spotting scopes. Somehow, though, Swarovski has managed to build a roof prism erecting system that does very little damage to the image quality of the scope. At the very highest powers, you can see just a smidgen of what I call roof prism softness in the CT75. The contrast is off just a bit, and resolution of the finest details seems, in direct comparison to, say, the Nikon Fieldscope 78ED, to be a just-barely-noticeable shade soft. In the field, the CT75 seems to have a slight edge, at high power, over the CT85, even though the CT85 equals the resolution of the current Reference Standard in the lab. The huge objective apparently intercepts enough more air turbulence to offset its extra resolution on all but most ideal days. At lower powers, either scope provides an exceptionally bright, snappy view with more detail than the average birder will ever need, but the 75's performance over its whole range, and its lighter, simpler, more compact package, probably make it, and not the 85, the scope the birder might want to seriously consider.
In the field, with the zoom attached, in the 20-45X range, the
CT75's larger objective and longer focal length allows it to equal
the performance of the current 60mm Reference Standard, the Nikon
Fieldscope ED, with the Nikon zoom, under almost any condition, and
with the added advantage of a very usable 45-60 power range beyond.
Given that it collapses to about the same size as the Nikon 60mm
scope, and weighs just a bit less, that makes the CT75 a very
tempting alternative.
For a real experience, you should try hand holding the CT75. Its long
tube and light weight allow you to brace it effectively (just like
the pictures of the old sea captains at the rail with their
telescopes) for fairly steady views at 40 power, and exceptional
views at anything under that. In a pinch you could pick out field
marks at 60X.
Draw tube scopes are not for everyone. They look decidedly odd on the top of a tripod, and some might find the fact that the eyepiece rotates as you focus bothersome (especially if there is a noticeable speck of dust on it). The whole focusing method, in fact, takes some getting used to and is undoubtedly slower than the standard knob or collar. To zoom the zoom you have to get a firm grip on the draw tube, or you focus instead of zooming. If you need a truly weatherproof scope, look elsewhere. Considering the CT75 in particular, if you want absolutely the highest quality views at any power, the Swarovski AT 80HD, or the Nikon Fieldscope 78ED, with their ED objectives, will still edge the CT75 out in direct comparisons, and the Tele Vue Pronto or the Questar will be clearly superior.
That said, consider what the CT75 has going for it: compact, portable, design; excellent optical performance; availability of an exceptional 20-60X zoom; and, very likely, the distinction of being the only birder using one, just about wherever you go. All in all, the Swarovski Habicht CT75 deserves a Product of Special Merit award in the Reference Set.