How Much Scope Does A Birder Really Need?

If you look at the new scopes coming out these days, it seems that everyone is playing catch up to Kowa. The Kowa 77mm Fluorite was the first scope to show a marked optical improvement over the Bushnell Spacemasters and Bausch & Lomb Discoverers (and the occasional Celestron C90) that dominated the birding field at the time. Oh, the Questar was always out there, showing just what kind of view was possible, but its price tag keep it out of the hands of most birders. Along came the Kowa, and suddenly you could have a view approaching the Questar for something like a third of the price. Many a birder took one look through the big Kowa and was never satisfied with his (or her) garden variety scope again.

Thus a trend was born. When Kowa had sold enough scopes to convince the accounting types that the big, $1000 scope with a semi&endash;apochromatic objective was viable on the birding market, everyone wanted into the act. We now have models from every major optics company except Swift (and can they be far behind?). If you have read the reviews in BVD or other publications, or had a chance to get behind one in the field, you know that these are exceptional scopes, capable of providing outstanding views. The latest crop (reviewed in this issue) are among the very finest optics I have ever tested or used. With single power eyepieces, they are capable of delivering a bird in the hand view at surprising distances, and of reaching as far out for the marginal identifications as any birder is likely to want to go. There are even two zoom eyepieces on the market now that will give you all the ease of use of your old Discover while amazing you with the detail and brightness of the view.

They are, however, big scopes. 77-80mm of glass and/or fluorite, a tube to hold the 480 or so millimeters of focal length, prisms big enough to contain and turn the light cone, eyepieces to provide sufficient power, field, and eye relief—it all adds up to a large and often very heavy package. Add the massive tripods necessary to support the things and hold them steady enough to get the benefit of their exceptional optics and you have a load that strains the limits of any birder's willingness, and some birder's ability, to carry them far afield. Then too, their size simply makes them harder to handle in all situations—harder to get into and out of the back seat (or, shudder, on and off a tour bus!)—more likely to snag in overhanging tree boughs—more likely to topple over in high winds—more apt to collect dings and scratches from the inevitable rough and tumble of field birding. The fact that so many birders do in fact carry them is testimony to how much a birder will put up with to get a really better view of the bird.

My question is this: is all that mass (and all that suffering) really necessary? Do we really need 80mm scopes?

Consider this: When the Kowa 77mm Fluorite came out there was a lot more going on there than just a big glass. It was among the first of the affordable apochromats—its fluorite element yielded obvious improvements in color rendition and clarity that simply had not been available up to then in any size objective. Kowa was also among the first to give serious attention to eyepiece design. Spacemaster eyepieces, in particular, have always limited the performance of the scopes they were attached to. Kowa's eyepieces (with the exception of their zoom) were big, sophisticated, and relatively expensive—worthy matches to the quality of the objective, and made a positive contribution to the performance of the scope as a whole. (The Kowa zoom is simply big and expensive. Anyone using one for anything other than low power views is not getting anything like the performance that the scope is capable of. Kowa should be ashamed of mating the thing with such a fine scope! This goes for most other zoom eyepieces sold for the big scopes. See comments in the Swarovski and Nikon reviews in this issue. Note too, while we are on the subject of eyepieces, that Celestron has now gone to full sized astronomical eyepieces for their C90. The Plossl now supplied as the standard eyepiece is a vast improvement over the original eyepieces and improves the performance of the scope markedly.)

What I am saying here is that a good deal of the performance gain most people see in going from a 60mm Spacemaster, or its like, to a 77 Kowa Fluorite, or its like, is due, not to the larger size, but to better objective and eyepiece design. Certainly the larger objective makes its contribution, in increased brightness and resolution, but to really assess that contribution you have to compare the big scopes to a 60mm scope using objectives and eyepieces of equal quality.

With the introduction of the new Kowa 60mm ED series, and, in particular, the new Nikon 78mm ED Fieldscope, we finally have a real chance to do just that.

The Nikon comparison is particularly revealing because the two scopes, 60mm and 78mm, use exactly the same eyepieces. I have been lugging both of them around in the field for several days, trying to get views of the same birds under identical field conditions, to make a fair comparison. About 95% of the time, you can see as much detail through the 60mm as you can through the 78mm. At first I really thought the 78mm had an edge, but that was because I was trying to compare the two scopes at the same power—setting the zoom on the 60mm at its maximum 45X and backing the zoom on the 78mm off until the image was the same size. I quickly discovered, however, that full power is not where the Nikon zoom is at its sharpest. Backing the zoom on the 60mm off until the reading on its barrel was the same as that on the 78mm increased the sharpness of the 60mm image and made it all but indistinguishable from the image provided by the larger scope, even though the image scale was noticeably smaller. By the same token, cranking the zoom on the 78 up to full power, yielded an image with almost exactly the same amount of usable detail as the 60mm at full power, even though the image was noticeably bigger and marginally brighter.

Consider this too: under real world conditions, it is often the transparency of the air that is the limiting factor in scope performance anyway, especially as distance increases and you are looking through more air. Heat currents, generated over the beach, over large expanses of water, or over open scrub land, bend and rebend the light passing through them, scrubbing away information, and leaving you guessing at the detail in the wavering, quavering, shimmering, fun house image that is all any scope is going to provide.

Now, I will admit, if I could afford the 78mm Fieldscope ED, I would not hesitate to buy it and use it instead of the 60mm Fieldscope. The 78mm Fieldscope is compact enough, and well enough balanced, to overcome most of my objections to big scopes, and I know I would enjoy the always slightly brighter, and sometimes slightly more detailed, image it is capable of providing. However, the 78mm Fieldscope is a special case. If it came to a choice between the 60mm Fieldscope II ED and any other big conventional scope currently on the market, I would choose the 60mm Fieldscope hands down. I would even choose the 60mm Kowa ED model over its 77mm Fluorite sibling. I would love to see what a 60mm Swarovski, designed to use the same excellent zoom as the 80mm series, would be capable of.

If, on the other hand, I knew I was going after birds out beyond reason—the wee and the far, way out there, where extreme high powers would be necessary—then I would want something like the Tele Vue Pronto, or even the Celestron C5 or Questar—something significantly better, or significantly larger (in objective size) and longer (in focal length) than any conventional scope. In my testing (see the sidebar on testing procedures) I found that conventional prismatic 80mm and smaller scopes reached their maximum resolution at about 60 power. After that, the image got bigger, but it did not show any more detail. The big mirror scopes, on the other hand, are still gaining detail at over 100 power. The C5, in particular, probably doesn't max out below 150X. If you want reach, bigger is always going to be better, but 80mm simply isn't enough bigger than 60mm to make much difference, especially when you are looking through prisms.

So, how much scope does a birder really need. I can only give you my opinion, based on my own experiences with many different scopes in the field. In most birding situations the best of the 60mm ED scopes currently on the market will give you all the performance you need, and all the performance you can actually use, at anything up to 60X. If you want to go a step up in optical performance from there, you are going to have to look at unconventional scopes like the Pronto. If you often feel the need of powers higher than 60X, you might as well skip right over the 80mm conventional models and go for something that is up to the job, and that means, almost certainly, a really big mirror scope.