(My spotting scope)
Scopes and rifle scopes. Just like binoculars, there are lots of scopes of various kinds and brands. And for different purposes, although their makers often try to create them versatile enough to be useful for general observations of both the heavens and the Earth.
For example, lightweight, compact and somewhat “fat” scopes, compared to their length, are mostly of the Cassegrain type, containing both optical mirrors and lenses. These have been adapted as spotting scopes, astronomical scopes and attached to cameras. There are many types of Cassegrains.
I built one that had three mirrors and no lens except for the various eye lenses. It was called (after the name of the original designer) a Dall-Kirkham Cassegrain. The main 12.5″ mirror was corrected to a concave configuration of an elipsoidal-concave shape with an F.L. (focal length) of 51.6875″, or F4.135 = 1313mm. The secondary, for increasing the overall F-ratio, was a 4-inch diameter convex spherical with F.L. = -20.04″. It was fixed at 13.9375″ inside the focal plane of the primary mirror giving an overall F.L. of 169.67″ (4309.6mm). Amplification by the secondary was 3.2826 for a final F/13.8. The usable part of the main mirror was 12.25″ due to a 1/8″ bevel on the edge for protection from chipping on the sharp external edge of the mirror. The third mirror was a flat 3″ diagonal (purchased) that turned the light beam at 90-degrees to the side of the telescope tube where a eyepiece mount for focusing was attached that held the various eyepieces for magnification and viewing. I had to study ray tracing and design, as well as depths and heights of curves on the front surfaces of the mirrors, then mount them precisely in a tube to make everything workable. From my notes at that time I’m told that the tube assembly (alone) with mirrors, focusing mount and spotting scope weighed 60 lbs. That was apart from the mounting assembly, to permit movement of the scope in any direction, which weighed an additional 50 to 60 lbs… not something you could pick up and move on a whim! In a permanent outside observatory, it was ideal, but for toting around the countryside, NOT! But both the mount and tube assembly had permanent handles for moving them inside whenever the weather was uncooperative. And the tube had dust covers at both ends.
The 12.5″ was given to a grandson, the 10″ was sold to a friend and I still have the 4.25″ RFT which is very portable, and gives first class daytime views as well as exquisite “rich-field” views of the heavens. Magnification can be amplified 3X by employing a Barlow lens in the focusing mount before inserting an eyepiece. I’ve had excellent views of the Orion Nebula and Globular Clusters under dark skies using this compact gem.
My Celestron C8 is called a Schmidt-Cassegrain (German and French combination) with a front lens of 8-inches of a specifically shaped glass to compensate for a spherical main mirror of 8-inches. The front part of the front lens is flat with the back side (inside the tube) of a very complex curvature that corrects any aberrations . The main mirror sends the light back to a convex spherical mirror of 2.75-inches that amplifies the f-ratio, sending the light back through a central hole cut through the main 8-inch mirror to a focusing mount that holds a diagonal mirror or prism in place (so you don’t have to stand on your head for viewing) and the eyepieces for magnification.
(You can see both the front glass lens and the main concave mirror. There is also a secondary convex mirror attached on the inside of the front lens. The adjustment screws for it are under the orange cover.)
There is also a commercial Maksutov-Cassegrain that is of Russian design, and more expensive to make due to the special glass and curves on both the front and back surfaces of the main front lens.
Lots of spotting scopes are made in these ways today, as well as lenses for cameras and astro viewing. Good ones are expensive. For cameras they, of course, tend to be smaller unless for professional use. For astronomical viewing, the sky’s the limit (pun intended). For hunting purposes, they should be ideal.
At one of the shops where I’ve done some business from time to time, a couple of years ago a Burris Schmidt-Cassegrain spotting scope was on display. The aperture of the front lens was 3.5-inches (if I recall correctly), and the overall length, including the eyepiece arrangement, was less than a foot. It stood on a comparatively small tripod that made it very stable. It’s weight was less than three pounds. I had a peek through it — it’s optics seemed perfect. Three and-a-half inch aperture is about 90mm (88.9mm). Try buying a 90mm spotting scope made up of lenses only, compare pricing, weight and viewing with that Burris (it’s not the only brand) and no doubt you’d happily spend the cash required for a Schmidt or Maksutov-Cassegrain. My 8-inch diameter Celestron is far too complex and heavy to tote afield for spotting game on yonder mountain, but I have set it up in our dinette for watching swallows build their nest and feed their young in the birdhouse provided in the NW corner of our back yard — I could even watch the ants coming and going on the pole supporting the birdhouse!
I watch a number of hunting videos on my computer, often late evening. In these, there are frequently spotting scopes in use by guides, outfitters and PHs. If it’s thick brush or at relatively short range, binoculars are used. But in mountainous terrain or open vistas, I see the pros, and sometimes the clients, dragging and wrestling with heavy spotting scopes on bulky tripods. I know that many of these scopes cost hundreds if not thousands of dollars! It reminds me of when I attended the auto races at Motorsport Park a few weeks ago — the pros, who were taking thousands of photos for promos, had telescopic lenses attached to their cameras that weighed upwards of ten pounds, were about 90mm to 100mm in aperture and nearly two feet in length! One set up beside me as we leaned on a wire fence for steadiness, my camera (the G9) weighed a few ounces, is 4″ x 3″ x 3.5″ (with lens fully extended). His pics were pro and mine were amateur, but the G9 has been used by many professionals! Mine was a gift from family, and secondhand. They bought it new at around $750. What do you think those ten pound professional’s camera scopes would cost? (Yeah, I know, I’m into cameras again, but I’m trying to make a point about “new” thinking and progress in the design and manufacturing of sport optics.)
(Eyepieces and amplifiers for my Celestron C8)
If you show up at the range with a “long-tom” scope, with the right name on it, to see tiny holes at 100, 200 or 500 yards, some will be impressed and ask questions about it (I’ve been a member at the same range for nearly three decades and know how these things work!). If it’s a 20 – 60 X 80mm, with a name like “Swaro”, how much did you pay?
Me? I paid $178 for my 20 – 60 X 80mm, and that was part of a gift from family on my 80th. And it works well enough to 300 yards (max at our range). The tripod that came with it was cheap, so I’ve mounted it on an aluminium camera tripod with extendable legs. Any limitation in viewing is the atmospheric conditions and mirage, not the scope.
I’ll not give the name, but it’s the one “despised” by the Elite! Previously, I used the same Burris 25X, 30mm for more than a decade. It was good enough to 300 yards for the 1/2-inch holes made by my .45-70 and .458 Win Mag but not for 30-caliber or less. As I’m currently shooting a lot of .22 rimfire at 100, the 80mm front lens is appreciated. And, yes, for anything else out to 300. Recall that during bright sunlit days, the human eye pupil only opens to around 2 to 2.5mm. So ideally, magnification should be about 35 – 40 times for best effect from an 80mm objective lens. For a 60mm about 25 – 30x, and for a 30mm, 15 to 20x.
Concerning RIFLE scopes, the optical principles are the same. The typical 3 – 9 X 40mm is no better than a fixed 4 power by 20mm unless the intent is to use it at 8x at dusk as each will have a 5mm exit beam of light that a good eye should be able to receive. The effect will be that the 4x will have a wider field of view but the 8x will resolve twice as much detail at the same brightness (The physics of that has previously been explained).
The basic issues involving rifle scopes are three: 1) Deciding on how much magnification is wanted or needed; 2) Brightness at that magnification; and 3) Toughness. That mostly has to do with the rifle cartridge to be used, and the overall weight of the rifle in action.
(On my CZ550 in .458 Win Mag was a fixed 4x by 21mm Burris with an eye relief of 5-inches!)
This is much like the same issues involving binoculars and spotting scopes — it’s mostly a matter of tastes and bragging rights. But also servicing. As mentioned, in Toronto is a main Bushnell office and service area. Their products have a no-questions-asked lifetime warranty. For myself that means a drive to Toronto to deliver the faulty or broken rifle scope (or binocular, spotting scope, etc.), and another drive to pick up the repaired part or a new replacement. It could be done by mail but I prefer to talk with them in person with the product in hand, and not wait “forever” for our mail system to work as it is supposed to. So, service for me is a primary consideration as most rifle scopes that take a beating from heavy recoiling rifles will give problems sooner or later– no matter the name or initial cost — especially after a few hundred rounds. And, on my .340 Weatherby I mounted a Bushnell Trophy 3 – 9 x 40mm for which I paid $100. It came off another rifle that was turned in at the same shop. It looked like new, out of the box. New price was $150. I put 1000 rounds through that rifle with that scope attached, with recoil over 50 ft-lbs per shot, and the scope was as good at the end of it all as when it was mounted. I now have a 3500 Elite 3 – 9 x 40mm on my 9.3 x 62 that generates between 43 and 48 ft-lbs recoil every time the trigger is squeezed. It did finish off a Burris before that! But I like Burris just the same. A Nikon 2 – 7 x 32mm is on my Ruger No.1 in .45-70. Most loads are over 50 ft-lbs of free recoil. I like the Nikon — so far no problems.
(The .340 Wea. Mag. with the 3 – 9 x 40mm Bushnell Trophy.)
John Barsness has tested just about everything that purports to be a sane choice for rifles, and his bottom line is that all of them, no matter the price tag or name that they bear is a guarantee against failure down the road depending on how many shots are taken and the cartridge used. It could be after a few shots or a few hundred. None have proven to be invincible. He prefers fixed power scopes, as do I, because there are fewer internal parts to go awry.
(The scope described below was at one time on my Ruger No.1 in .45-70 IMP. Now, there is a Nikon 2 – 7 x 32mm shotgun scope on it — see the header.)
I still have a fixed 4x by 20mm silver Safari Burris that I purchased over twenty years ago. It has been on just about every “hard kicker” I’ve ever owned, including numerous .45-70s, a .458 Win Mag and now a 12ga magnum shotgun. Somewhere early on, the crosshairs went out of focus. With my extensive background in eyepieces, many of which I’d disassembled and reassembled to understand how they worked, I removed the retaining ring that held the first acromatic lens in place, removed the lens and spacers, adjusted the distance between lenses, screwed the retaining ring back in place and the crosshairs were in focus with the field of view! Never has there been a problem since. The idea of nitrogen purging to keep out fogging-up is mostly a myth. That scope has never fogged, nor have any astro eyepieces that I’ve tinkered with in a similar way. My first binocular, the 10 X 50 Bell and Howell has had the right eye lens removed on numerous occasions, the various lenses removed and reassembled in a different order to give a higher magnification and wider angle, That eye lens has never fogged or given any kind of distortion to the very edge of it’s field of view. I DON’T RECOMMEND THIS BE DONE BY ANYONE ELSE WITH ZERO EXPERIENCE WITH EYEPIECES, but I’ve done it on countless occasions to give different effects and learn about eyepiece construction.
That particular Burris, fixed 4x, was sold to me at discount because “they” sent the wrong scope to the store… not the one ordered for a client. At that time, the retail price marked on the box was about $365 (That was a lot of cash nearly thirty years ago!). I got it for $265.Since the repairs I made, it has never let me down in the sense of expectations for a 4x by 20mm.
I’ve written as I have just to say that name brands and price tags might mean something, but not everything when it comes to optics for cameras, binoculars, scopes and rifle scopes. Down the road, I might buy a product from Burris again, but then maybe not. That same applies to any brand. I had a fixed 4x by 21mm Burris on my CZ550 .458 Winchester Magnum. Never a problem, but the long eye-relief of 5-inches on both of those Burris’s on heavy recoiling rifles sure gave real comfort of mind!
That’s all for now…
Til the next,
Shalom
BOB MITCHELL
Lovin' The Big Bang 