Pentax 80mm Ed Spotting Scope




I have always wondered what would happen if an optical company designed a spotting scope from the eyepieces forward, rather than the objective back. Many birders are surprised to discover the limiting factor in a spotting scope’s performance is, most often, not the big chunk of glass out front, but the little lenses in the eyepiece. All the objective lens has to to is to form a tiny image of the bird, an image that floats in the air within the tube of the scope. In order to see the image, you have to hold a magnifying glass, the eyepiece, up to it so that you can get your eye really close and see all the detail. Of course the objective has to be up to the job. The size of the objective determines both the brightness and the theoretical resolution (amount of detail) of the image formed. The quality of the objective determines the actual resolution of the image, and both the contrast of the image (it snap) and its purity of color. That is the reason we are seeing so many 77-82mm ED or Fluorite scopes in the field today. The big objective provides a bright, highly detailed image, and the exotic lens material provides the best contrast and color fidelity available. However, you still have to look at the image formed by the objective with that little magnifying glass, that eyepiece, and, if your eyepiece is not what it ought to be, it doesn’t matter how bright or how detailed or how contrasty or how true the image is, you won’t be able to see and appreciate it.


And eyepieces are not easy to design. Besides determining the magnification of the scope (20 times the naked eye view up to 60x or even 80x), the eyepiece has to yield as wide a field of view as possible so you can find and track the bird easily and as much eye relief as is possible, so you can view comfortably. A simple convex lens, like any magnifying glass, would work, but, at the powers we ask for in a scope, it would produce a view of the image (and the bird) that was obviously distorted (bent out of shape, especially at the edges) and very narrow, and you would have to have your eye practically right up to the glass to use it. Not to mention that all the effort and expense that goes into exotic lens materials in the objective is wasted if the eyepiece introduces its own false color.


Think of it this way: objectives use a lot of glass but they are relatively simple things. They are made out of two kinds of glass (or sometimes some other transparent material, like Fluorite), glued together in a single element. They generally only have four shaped surfaces, four surfaces which have to ground and polished to perfection. It is a relatively simple design problem. (A few of the best objectives may have three pieces of glass in two elements and, therefore, six surfaces.) To begin to match the quality of that objective, to balance power, field of view, and eye relief, in a design that is well corrected for distortion and color, the simplest eyepiece regularly in use in a spotting scope, and the most common, is as complex as the best objectives. It has six shaped surfaces, in two different elements, and employs two different kinds of glass. To optimize power, field, eye relief and correction, you generally have to use up to seven elements, several of which are made of two different kinds of glass—in complex designs that will have 14 to 24 shaped surfaces. Even if you set out to design an eyepiece worthy of your objective, the cost of designing and producing such a lens is often beyond what a manufacturer thinks the birder is likely to want to pay. Makers know that big fancy objectives sell scopes. It is very difficult to get most birders excited about eyepieces, or to convince them that they might have to spend as much for the little eyepiece as they paid for the whole rest of the scope.


Therefore, until recently, it has been the eyepieces that have limited the performance of high quality spotting scopes. I have often said, here at BVD and elsewhere, that if you are want a zoom eyepiece on your scope, you should shop for the eyepiece that meets your needs, and then buy the scope it fits on. There are still only a handful of truly usable zoom eyepiece available for spotting scopes. There are a few that are good enough so that it is worth buying the scope they fit on. (Okay, they are, in ascending order (saving the best for last): the traditional zoom for the Nikon Fieldscopes; the Japanese “Swarovski look-alikes” available for the Kowa, the Swift, the Celestron, the TeleVue Ranger, and now the Bausch and Lomb Elite scopes; and, still the best, the Swarovski itself. Leica redesigned their zoom eyepiece recently and improved it considerably, about to the level of the Nikon zoom, but still not in the Swarovski class.)


There are a few other outstanding eyepieces out there that make the scopes they fit on worth owning. The Leica 30 power wide field eyepiece is simply wonderful, and the 30 wide for the Nikon Fieldscopes is not far behind. I haven’t tested the fixed wide eyepieces for the Kowa, but I hear they are also fine. Still, truly great eyepieces are few and far between.


All of this is by way of introduction to the new 80mm ED spotting scope from Pentax. You see, Pentax already produces a world class set of eyepieces, designed for amateur astronomy. There is pretty general agreement in that community that the Pentax astronomical eyepieces set the current standard, or at least equal the current standard, for a useable combination of power, field of view, eye relief and correction (all of which are just as important to an astronomer as they are to a birder). They are currently the eyepiece to own if you are serious about visual astronomy. These are “no holds barred” eyepieces, each one the size of can of condensed soup, with lenses about the size of the objectives in most mid-sized binoculars (in fact, if you took the glass out of the Pentax eyepiece barrel, you could just about slide the whole Swarovski zoom, body and all, right inside, and the Nikon zoom would rattle around inside even the smallest of the Pentax light paths). They cost, generally speaking, all by themselves, as much as a good pair of binoculars too. Of course, they are astronomical mount eyepieces, made to fit in the 1.25 inch standard astronomical focusers. They don’t screw in or twist on, they slide into an open tube and are generally locked in with a set screw.


What Pentax has done is to design a spotting scope suitable for field use by birders to fit these eyepieces. They started with a clever rotary locking mechanism that allows you to just slide the eyepiece in and twist a large knurled ring to lock it. They waterproofed the main body of the scope (the eyepieces were already waterproof). They built an elegant, and fairly standard looking spotting scope focusing mechanism. They added an very nice pull out sunshade and some attractive armoring. Last but not least, they designed an excellent, long focal length, 80mm ED objective to put up front. The result, with one of those big eyepieces on the business end, is relatively large scope, but they have managed to keep it within the weight range for other 77-82mm scopes.


Was it worth the effort? Optically, the new Pentax scope, with its fixed power eyepieces, is noticeably superior to any other scope currently on the market. Yes, you read that right. The at 30 to 40 power, the Pentax scope equals the resolution of the previous Reference Standard for all scopes, the TeleVue Ranger, and it has a notably brighter, more contrasty image with more intense colors and sharper color separation. The field of view and ease of use has to be seen to be appreciated. These eyepieces are everything the astronomers have claimed. The field is wide and open. The eye relief allows an exceptionally easy view from behind the scope. It is not like looking through a scope at all. It is like walking right up to the bird and looking at it through the highest quality magnifying glass you have ever seen. And did I say the image was bright? The huge light path of these eyepieces, beginning with the 1.25 inch tube, optimizes the light gathering ability of the 80mm objective. You suddenly realize that most other scopes are being “stopped down” from the true objective size by the tiny eyepiece barrels we use on them.


So okay, Pentax has managed to create a spotting scope worthy of their world class fixed power eyepeices—but they didn’t stop there. New with this scope is the first “waterproof” zoom eyepiece. It is huge—a size bigger even than the fixed power eyepieces, and, again, features a light path the size of the 1.25 inch mount. While it doesn’t have either the field of view or the eye relief of the fixed power eyepieces, it certainly equals or exceeds the field and eye relief of the zooms available until now. Combined with the 80mm ED objective of the scope, it provides an amazingly bright, amazingly sharp, amazingly detailed view from 20 to 60 power: the best overall performance I have seen so far in any spotting scope with a zoom eyepiece. It has just enough eye relief so that I can see the whole field at all powers. This zoom is a truly impressive accomplishment.
Impressive as the zoom is, don’t forget to take a look at the view through the fixed power eyepieces. The 30x eyepiece is bright enough and sharp enough so that you would rarely need higher powers, and so easy to use that you might not ever want to take it off.


Last but not least, Pentax has managed to put this scope together at price that is certainly competitive with the other major players in the premium scope market.


In fact, the combination of fairly conventional spotting scope handling, reasonable weight and excellent balance, a measure of field durability and weatherproofness, a big bright objective, reasonable value, and what are simply the finest eyepieces currently available for any scope on the market make the Pentax scope the current Reference Standard, not only for conventional spotting scopes, but for all scopes. I have no hesitation in saying the Pentax scope is currently the best birding scope you and buy at any price, and, given its price, might even be considered a bargain.