I’ve had an interest in many things: I loved my experience as a deep-sea fisherman. As per my last article, I became a builder of astronomical telescopes (better viewing than my commercial Celestron 8 because they had larger mirrors, except the 4.25-inch RFT) and a member of The Royal Astronomical Society of Canada. I also enjoy auto and motorcycle races, as well as touring motorcycles which I was involved in for several years. Then, of course, hunting and shooting, and other outdoor recreation (camping, hiking and fishing) have always been main sources of staying healthy. Christian music has also been a major part not only of training and ministry, but within our extended family it has been a preoccupation both in vocal and instrumental arrangements. “But what do you have that you have not received?” (as a gift from God) — the Apostle Paul.
(Ooops! How did that get in here? Hey, that’s my old Gold Wing… but who’s that in disguise on the back? Could that be my wife of thirty-two years ago? In just five days we will have been married for sixty years! Unbelievable!)
As to our main subject, in my possession are five binoculars and one monocular. In addition, I’ve given a 7 x 35mm to my wife and an 8 x 40mm to a daughter-in-law. These were accumulated over a period of about 1/2 century.
Why do I choose binoculars over monoculars, since I can only benefit from the left side of a binocular? I’ve been rarely asked that question, but on a few occasions it has come up. It’s simple: binoculars are made better, have better optics, balance better, can be held naturally by both hands, have a much greater variety in sizes, shapes and models — greater dollar value. Plus, others have looked through my binoculars to get an even better view than possible from a monocular.
Another “trick” is this: I have on occasion adjusted the left side for general viewing and the right for specific views. I simply move the binocular left to view through the right lens something too close for general viewing. As an example, in watching birds at our closest feeders that are only a few yards away along the fence to the north side, I may adjust the right eye lens for those views without refocusing the whole binocular. Our back fence and the trees just outside that fence line to the west make excellent perches for birds as well, so I may just leave the binocular focused for the back fence area (farther away), and the right eye lens for some feeders close at hand. Otherwise, I’d have to constantly refocus the whole binocular if “chasing” birds from the west side to the north side of our property.
OK, now for specifics: My first binocular, as mentioned in the previous blog, was purchased at a camera store in Montreal in the mid ’60s for wide-angle views of the heavens. I still have it. It’s a BELL & HOWELL, 10 x 50mm, and heavy! Great for steady viewing but arm weary if standing. The best is to use a lawn chair that folds nearly flat, point it at the heavens and relax. But it makes a great bino for birds as well. It’s just too heavy and bulky for toting afield for hunting.
The several I’ve given away fit in here next. The 7 x 35mm, which I gave to my wife, was actually second. It’s a Tasco that has excellent structure, balance and very good optics. I used it for several years as a hunting optic, and it’s near perfect for that purpose. My wife uses it for birding. It is still in it’s original case.
Both of those binoculars have poro prisms which sends light through two sets of prisms in a zig-zag fashion that tends to make them heavier than those with roof prisms where the “barrels” are straight line without a crook in them. Both types have some advantages, the poro prism type being cheaper, though today’s roof prism type are more common and less costly than in the past, with better optical quality than when first introduced.
The case for the 10 x 50 Bell & Howell gave up the ghost long ago, though the binocular is in great condition and equals some of today’s best optics at eight times the value! In the ’60’s, it cost $75, which was a lot of money then — today, about $500 – $600.
Then, around twenty-five years ago, came another 7 x 35mm Tasco, one that has a fixed focus. It’s tough, and made in Japan in the ’90’s. It rarely, if ever, has been brought inside the house. Always, it is left in a vehicle for all seasons. And it never fogs. I don’t worry about it and in an “emergency” I could always find it somewhere in my van or currently in the CSUV (Compact SUV). So, I’m never without a binocular that’s somewhere handy. Yes, I know, it’s abused in ways that I would never treat my “high-end” binos. And still in it’s original case.
In the last dozen years, or so, I’ve added three more… one of exceptional class, and two “cheapies”. But don’t be fooled by those typical designations. As it turns out the “cheapies”, from a practical standpoint, are about as good as the high-ranking one! I’m sure there’s a lesson to be learned in there somewhere.
What lesson? You don’t have to believe me, if you don’t want to, but John Barsness on 24hr Campfire, makes a lot of practical sense in the Optics section. Amongst other things, he’s devoted much time, energy and expense in researching and studying such trivia. If you’re a member there, go there.
However, I’m not exactly without experience either when it concerns certain optical applications. Having built six telescopes of the reflecting kind; one a compound (12.5″ diameter telescopic mirror, plus a 4″ convex spherical secondary) and a 4.25″ RFT (Rich Field Telescope), another 12.5″ RFT and two 10″ Newtonians as well as finishing a third 10″ for a friend, who being a master craftsman did the mount and tube, and ground the Pyrex mirror to the correct concave depth, and polished it. I did the final correction of the glass to form a parabolic concave shape from a spherical concave shape. That correction was to 1/10 wavelength of light or better. That’s throughout the whole front surface of the glass which became the reflective mirror when a very microscopic-thin coat of aluminium was applied (In a reflecting telescope the light does not pass through the glass but is reflected from the front concave surface). You can’t measure that with your typical ruler or draftsman’s tools. And just to get a perspective on 1/10 wavelength of light — that’s about two-millionths of an inch! I’ve managed all that with proper equipment and know-how. The two 10-inch, two 12.5-inch and the 4.25-inch had to be corrected to at least 1/8 wavelength of light, and 1/10 is better, which, by God’s good grace, I was able to achieve. The first 10-inch was made of porthole glass that was too thin and would not adequately hold it’s parabolic shape so was ditched for a proper Pyrex blank of 1.5-inches thickness that resisted any kind of distortion due to it’s own weight or thermal conditions.
All of the dimensions given above have reference to the diameter of the mirrors, not the length of the scopes. The two 10-inch scopes were F7.7, or a focal length of 77 inches (1966mm). Tubes for holding the main mirror, and the secondary diagonal mirror, plus the eyepiece focuser, were about seven feet in length. They were made from Sono tubes used in construction to pour cement into, and for the 10-inch telescopes were 12″ inside diameter. The inside was painted matte black and the exterior had multiple coats of fibreglass impregnated with coloring.
To make such telescopes steady and manageable, the mounting system had to be rock solid and very heavy. The whole outfit could be brought outside (and back indoors) by making the seven-foot long telescope removable from the mount. The mount itself, with handles, could be tipped and rolled inside on it’s two heavy-duty wheels. The 12.5″ actually was much shorter being a compound telescope (something like the Celestron) with a special built tube of about 15-inches diameter.
The reason the mirror has to be a parabolic shape is so all light rays that form an image focus to the exact same point where the eyepiece can magnify it. The diameter of the mirror (reflecting type scope) or the objective lens (front lens) of a refracting scope, determine the practical limits of magnification, which is about 60X per inch diameter (50x practical limit) of the objective lens or mirror if the atmosphere allows it. When a small refracting scope of 60mm/2.4″ diameter of the front lens is advertised to give more than 60x magnification per inch diameter, don’t invest in it… that’s false advertising! 60 times 2.4 = 144 times magnification. Beyond that the image can be magnified to 300x if you want but that is like blowing up a photo to the point where you couldn’t discern even what the photo represents. Plus, at that magnification, the rotation of the earth would appear to be increased by 300 times… also any vibrations! So, even at 144x, images appear to be moving across the eyepiece field of view very fast — unless one has a very solid mount with a motor drive to correct for the earth’s movement. Even a 10x binocular that is not mounted solidly to a stand or table, but hand held, will magnify any hand or arm tremors, and unsteady body movements, by 10 times! And that, of course, applies to scopes as well.
And another fact of optical magnification, especially if viewing horizontally, is that views are often greatly affected by atmospheric conditions. I’m sure you’ve had the experience on a hot day of the image bouncing around or being broken up by atmospheric turbulence, or mirage. That’s heat rising from desert sand, a paved road or roofs of houses and other buildings. The air we breath is also a lens many miles thick that is in constant motion. That’s why astronomical observatories are usually built far away from cities (and their lights) on top of mountains. The atmosphere is very “thin” up there. I’ve had nights when it was possible to use the full potential of my telescopes on planetary and lunar detail at 600x magnification, but those nights are extremely rare, something like one in fifty. On other nights, with the same scopes, 100x was really pushing matters. But on those crystal clear nights when the stars were “twinkling”, it was best for low-power viewing of nebula, star clusters and wide angle views. The twinkling is caused by very turbulent cooler air moving in to replace the warm air rising from the earth, buildings, etc.
I’ve had to purchase multiple eyepieces for those scopes. Then, with my 8-inch Celestron, I inherited five very expensive eyepieces (by which you examine the image formed by the front lens or mirror). I’ve literally spent thousands of hours looking through such eyepieces to examine extremely minute details in star clusters, nebulae, and details on the moon and planets. Some insist that has nothing to do with scopes and binos for hunting. Really! How did they come to that false notion? Have they spent thousands of hours looking through both? You DO learn some very important details from such experiences. Let me tell you how.
The diameter of the objective lens (or mirror) determines not only the amount of light entering the scope or binocular, but the resolution of detail as well, assuming proper construction and correction of the lens (or mirror). And today, even very cheap binoculars have excellent optics. It’s not the price of, or the name on the binocular that determines resolution. There’s a matter of optical physics that says you can’t get more light rays into your 35mm binocular than a 40mm. The 35mm bino has only 76.6% the light gathering ability as a 40mm, and only 87.5% of it’s resolution ability. Those are optical facts assuming each is correctly made as achromatic lenses, and have anti-reflection coatings that permit from about 97 – 99% light transmission. If we make the difference in objective lens (front lens) diameter greater, for example a 30mm vs a 50mm, the results are even more dramatic in favor of the 50mm. A 50mm has 278% greater light gathering ability than the 30mm, and 167% greater resolution, assuming, again, proper construction. But the 50mm will likely be around 2 – 2.5x heavier!
Another point to keep in mind, however, is what do we want to do with our binocular(s)? I have the 10 x 50mm, a fixed focus 7 x 35mm (Tasco), a roof prism 8 x 42mm Tasco, a 10 x 40mm Bausch & Lomb National Audubon Society edition (poro prism), and a 10 x 25mm Tasco (roof prism). (And, oh yeah, a VERY cheap, made in China Bushmaster 10 x 25mm roof prism type that I wouldn’t even recommend for kids!)
Costs? Apart from the 10 x 50mm B&L that was about $75 as mentioned, the 7 x 35 fixed focus, the 7 x 35mm given to my wife (Tascos) and the 8 x 40mm given to a daughter-in-law, I don’t recall what was paid for them. That was quite a few years past. The 10 x 40mm B&L was a warranty replacement for a 8 x 40mm Bushnell (poro prism) that I paid around $300 to obtain. It’s internal (plastic) baffles warped while left in my car in the heat of summer! In Toronto there’s a Bushnell office and repair under warranty shop (I’ve used it quite a few times for rifle scopes! They either fix it or replace it at no cost.). They offered me one of two as a replacement. I chose the B&L that was worth a lot more than what it replaced! The 10 x 25 Tasco was bought about three and a half years ago at a “big box” outdoor store in Oshawa for the huge sum of $12.50, marked down from $25! There was a big wire basket full of them in their small cardboard containers. I thought “What the heck…”. It turns out to be the bino I most use in both birding and hunting! And it has a neat little case that attaches to my belt. Later, at the same shop, they had a sale on the roof prism 8 x 42mm Tasco, marked down from $59.95 to $29.95. Of course, I always take a long look through them before purchase, and I bought it. It goes with me a lot, and is about as good as the 10 x 40mm B&L. It’s optics are excellent! I test all of ’em on the birds at our feeders.
(My wife bought this range finder for me as a Christmas present a few years ago. It works perfectly. So far, the maximum range at which I’ve used it is 562 yards. It’s a practical tool. Cost? $99.99 at Canadian Tire — plus tax of course!)
Tasco is one of those names considered by “elitists” as unworthy to even be pronounced by their lips! In “early years” of it’s history, it’s products were considered very good, if not best. Tasco went through a period of poor quality in its offerings, so many still despise the brand without giving it a fair chance. Bushnell bought the company, and the products are now second to none in my experience. I have three binoculars, a “high-end” rifle scope and a laser range finder all bearing that name since Bushnell took over the company, and I could not be happier considering quality and price! I’m no where near being, or becoming an “elitist” in such matters. But that is why I gave some of my credentials re: optics. I have two complete sets of very expensive eyepieces for my Celestron C8, plus two Barlow lenses that double and triple magnification of the eyepieces.The Tele Vue Plossls alone are worth more (each) than paid for any binocular except the B&L, so I’m not exactly dumb in regard to eye lenses. And the Tasco eye lenses in my binos are as good as most high-end optics! Put another name on them and they could pass as “Euros”.
Regarding resolution of detail: As mentioned, the larger the objective lens, the greater the potential for resolving finer detail. But that also depends on magnification. For hunting purposes, magnification and light gathering ability are most critical because we aren’t examining a 1/4 mile crater on the moon! But as darkness approaches, the exit pupil from a binocular should be at least 4mm, and better still at 6 or 7mm. And magnification should be at least 6x to see enough detail to determine if this is the animal we want to shoot, or not. Why 5 to 7mm exit pupil? Let’s define “exit pupil”: It’s the size or diameter of the beam of light that exits the eyepiece (the part you look through). During bright sunny days (as might be the case in Africa), the pupil of the eye will close down to about 2 to 2.5mm. If the beam of light is 5mm only 25% of the available light will enter through the eye pupil. At dusk, just after the sun has set, the pupil will dilate to about 5mm to let in more light, and can effectively use a 5mm beam of light from the binocular. With a couple of minutes of legal light remaining (nearly dark), the pupil will yet expand to 6mm, or even 7mm in healthy eyes (why “night glass” binoculars are either 7 x 50mm or 10 x 50mm). The diameter (size) of the beam of light coming from the binocular eyepieces is determined by the front lenses diameter (say, 40mm, for example) divided by the binoculars magnification (say, 8X), in which case the beam of light would be 5mm, if your binocular should be an 8 x 40mm.
(Diameter of the eye lenses is a clue to the practical value of the binocular — Center B&H = 22mm; L to R: 7 x 35mm Tasco = 15mm; B&L = 18mm; 8 x 40mm Tasco = 20mm, and 10 x 25mm = 12mm. But you can’t have wide angle, high power and long eye relief in the same binocular or scope. The fields of view in angles are from 75*in the 7 x 35mm fixed power and about 60* in the B&L.)
So, as a rule of thumb, the best hunting binocular for daytime general use, including dusk to almost complete darkness, would be a high quality (NOTE: I DIDN’T SAY “HIGH END”!) 7 x 35mm roof prism type (roof prism types are usually lighter) that will still give a 5mm light beam to cover all conditions adequately. An 8 x 40 would be my second choice, though it will be heavier. I’ve used my 10 x 25mm quite a lot in hunting because it’s good enough for daylight viewing, and because it’s very lightweight, but it’s about useless when looking for bear as darkness approaches. And let us not forget that our eyes are lenses too. In the end, their condition is priceless! Are you thankful for yours? My one good eye has value well beyond all the binoculars of the world heaped together, because the most elite among them couldn’t begin to replace the value of my left eye.
In my experience for hunting, a lightweight 8 x 25 or 10 x 25 is perfect until near darkness. Then more light is needed, something like a 7 x 35mm or 8 x 40mm. Most brands today are perfect enough, but keep the weight down. Many, like other optics, are made in the same plants, or the same country, they just have a different sticker on them.
And all of that in 3000 words has been reduced to one short paragraph of 56 words, which would suffice for most readers who just want an opinion. Then, they would check opinions on the forums where many would tote “high-end” Euros that would cost $1000 or twice that… but would give no more “light” (understanding) on the matter. But a few, like myself, just want to know why. Why? It’s “name dropping”, that’s why.
‘Til the next on scopes… Yeah, rifle scopes too!