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IHMSA News Feature Article
Published in The IHMSA News, the Official Publication of The International Handgun Metallic Silhouette Association
Published monthly except November/December - January/February
IHMSA on the web at http://www.ihmsa.org
 
Weaver's 90mm Green Giant
By Todd Spotti
 
     I was blown away at last yearís Shot Show when I saw a prototype of a new 90mm spotting scope from Weaver - the ETX. It looked identical to Meadeís 90mm astronomical telescope, but at the same time it some how looked different. (As you know, Meade, the largest manufacturer of amateur astronomical telescopes in the world, bought Weaver, Simmons, and Redfield in 2003.) As I looked the ETX over, it suddenly hit me. The scope wasnít attached to the usual motorized fork mount that tracks the movement of the stars as they move across the night sky. It was simply screwed on to the top of a sturdy tripod just like a regular spotting scope.
 

     In addition, the scope body was decked out in traditional Weaver emerald green instead of Meadeís dark blue. It was also one of the most impressive anodizing jobs Iíve ever seen. That green scope tube looked like it had a couple of layers of clear coat on it. I know it didnít, but it was gorgeous never the less. I also noted that the Weaver was fully multicoated, including the eyepiece lens. However, the biggest surprise of all came when the Meade marketing rep told me that the scope would sell for around $300 - far, far less than what the astronomical version costs. I was honestly stunned! I thought the price would be around $800 to $1000. I couldnít help but blurting out ďThis is one fantastic bargain.Ē The rep wore a proud smile that was a mile wide.
 
     Astronomy is one of my other outdoor interests and so I was already very familiar with the catadioptric design of the new Weaver. I also knew that it is the most technically sophisticated design for a terrestrial telescope that there is. Consequently, I was confident that this scope was likely to have a level of performance that was going to make the competitionís hair turn gray. As it turned out, I was absolutely right.
 
     So what is a catadioptric telescope? Itís one that uses both mirrors as well as lenses to produce an image. And so why is that a good thing? Because by using mirrors, the light entering the telescope can be reflected or ďfoldedĒ back and forth multiple times to increase the focal length of the telescope without increasing its overall physical size. When you increase the focal length of a scope, you increase its magnification potential. Indeed, Weaver says you can read license plates a half mile away with an ETX.
 
     Primitive straight through refractor type telescopes from yesteryear used to be immensely long. (Iím talking even up to tens of yards here.) As a result, they were extremely expensive and cumbersome to use. Even modern, research quality refractor type telescopes can be pretty long. However, by folding the light path, the physical length of a scope can be radically shortened while achieving a long focal length at the same time. So it was no surprise to see that the Weaver 90 ETX has a focal length of 1250mmís (48.75 inches) while the overall length of the tube is only 11 inches.
 
     So how does the ETXís folded optical system work? Ok, up front we have a huge, 90mm, Maksutov type lens. (BTW, this type lens design has a well earned reputation among amateur astronomers for clarity.) Now light reflected off the ground, the trees, from the the sky, etc., etc. is hitting that lens from every angle imaginable. The function of the Maksutov is to force all those photons into nice, orderly, parallel rows going down the length of the scope. Consequently, the front lens on a catadioptric is often referred to as a corrector plate.
 

 
     Now, those nice orderly rows of photons proceed down the length of the scope and hit a mirror attached to the rear. The light path is now reflected and focused back up front to another smaller mirror that is attached to the back of the front lens. The light path (containing the image) now is focused into a narrow column and is again reflected back towards the rear down into a black tube mounted in the center of the scope. The purpose of the tube is to act as a baffle and provide further insurance that stray light from the sides isnít going to mess up that pristine image thatís being sent down the center. Once the image reaches the rear, it hits a 45 degree prism that turns the image right side up and into the high quality fully multicoated Plossl eyepiece for your viewing pleasure. So you see the light path is folded multiple times before it comes out of the end.
 
     On a tour of the Meade factory last December, I had a chance to see the mirror and lens grinding and polishing operation. I was absolutely stunned at the precision in which it was done. While itís impossible to produce absolutely perfectly shaped lenses and mirrors on a mass production basis, Meade comes very, very close. How close? The Senior Vice President for Production explained it this way. He showed us an eight inch mirror blank. He said if you were able to magically increase the diameter of the blank so that it was now a mile wide, the variation of the surface from absolute perfection would only be equal to the thickness of a credit card! That degree of exactitude is amazing.
 
     Let me make another important point. Each front lens and rear mirror is perfectly matched to each other. So whatís that supposed to mean? As a hypothetical example, if you have a mirror with a surface thatís minus a quarter of  a wave length variation from perfection, it will then be matched with a lens that has a surface that measures plus a quarter wave length. 

     The differences between the two now cancel each other out, and for all practical purposes, you have an optically perfect system. 

     As I toured the Meade factory, I actually saw several large shelves stacked with mirrors and front lenses that had been measured and paired to each other. No other standard type spotting scope does this, no matter how much it costs, or how difficult to pronounce its name. Needless to say, I was extremely impressed with Meadeís technology and commitment to optical perfection. 

     Let me say up front that this type of spotting scope is very different than the normal spotter that weíre accustomed to working with. First of all, this isnít a sealed, nitrogen filled, shock proof, water proofed, rubber armored product. As such, and because of itís size, itís not really suitable for being taken into the field on a hunt. However, the lack of those characteristics doesnít prevent it from doing a clearly superior job in the more benign environment found at a shooting range. 

     Another characteristic of this particular type of scope is that magnification is controlled by switching out  removable, drop in eyepieces. To change magnification, all one has to do is back off a set screw with a little knob on the end, pull the lens out, and insert another lens from a large selection available from Meade or any number of other suppliers. Tighten up the set screw and youíre ready to go. The ETX 90 comes standard with a 26 mm eyepiece which provides 48X in magnification.

     By and by I got one of the big Weaverís out to the range and started to put it through itís paces. I immediately ran into an unexpected situation. The 26mm eyepiece combined with the 1250mm focal length produced too much magnification and too narrow a field of view. When I trained the scope on the 50 meter chicken target, the only thing I could see was the very center of the animal i.e. no head, no tail, no leg etc. However, I could see every little dimple, crater, scratch, bump, etc. with amazing clarity. The resolution was absolutely stunning. It was almost like looking at the surface of the animal with a microscope. Unfortunately, a super narrow field of view is not a desirable characteristic for a spotting scope. I then moved the scope to the 100 meter pig, the 150 meter turkey, and the 200 meter ram. Even at 200 meters, I couldnít get the whole animal into the image. Well this wouldnít do. 

     I then got an inspiration. I own a Meade 8Ē diameter astronomical telescope that uses the same type eyepieces as the Weaver ETX, and I had a fair number of them at home. When I made my next trip to the range, I included a Meade 40mm eyepiece in my Uncle Mikeís range bag. This lens produces around 30X of magnification versus the 26mmís 48X and the field of view is much wider. When coupled with the ETX, the 40mm lens produced an even more brilliant image, a very nice field of view, and 30mmís of eye relief. (On some other spotting scopes, youíll get only somewhere between 7 and 12 mmís of eye relief.) The 40mm lens made all the difference in the world in the scopeís performance. When pointed at the 200 meter ram targets, around two and a quarter animals presented themselves in the 40mmís eyepiece which is more than wide enough. Even when pointed at the chicken, the whole animal and at least 6Ē of space around it was clearly visible - plenty of room to see a miss unless the shot was just fantasticly wild.
 
     When Meade/Weaver says that you can read license plates a half mile away with the ETX, I believe them. The resolution or clarity/crispness of the image with the 40mm Meade lens is the best Iíve ever seen in any spotting scope - no matter what the cost, and I donít say this lightly. As you know, Iíve reported on a lot of spotting scopes over the years that produce excellent images, however I can definitely say that the image in this scope is the very best Iíve ever seen by a substantial margin.
 
   As previously reported, I usually do my resolution evaluations at 50 yards. (Some optical manufacturers do their testing at 25 yards or even less.) Well, when I did my 50 yard evaluation, the result was interesting to say the least. The resolution was so good, I could actually see imperfections in the printer paper that I had used to produce my standard home made resolution chart. I then moved the chart out to 100 yards. The green giant was able to easily resolve the smallest line on the chart (9 point) without even breathing hard. This was way too easy.
 
     I then took the scope to the LA Silhouette Clubís November match, where it was an instant hit with several people oohing and ahhing over it. It was also the perfect place to do some practical viewing exercises with the scope. The clubís range is set in the foothills of the local San Gabriel Mountains. One of those foothills is directly behind the 200 meter line with increasingly larger foothills further beyond. As it turned out, at the very top of one of the more distant foothills, perhaps a mile away, is a lone yucca plant - a type of succulent/cactus. In the center of the plant is a stalk about 3í high with a flower at the top. That stalk is perhaps an inch and a half wide, and yet the Weaver was able to resolve it with no problem. In fact, the Weaver was also able to resolve individual blades of grass around the yucca plant and even a weed called fox tail which is very common in the West and which resembles wheat. People were amazed as fox tail stalks are only around an eighth to a quarter inch in diameter! Just think of it. A quarter inch resolution at one mile. Iíve never seen spotting scope performance like this - ever.  
 
     One last technical point - the scope will actually focus down to 12 feet. Amazing! This means you could use it for everything from airgun to 500 meter silhouette. I love versatility - especially when itís coupled with outstanding performance.
 
     The price of the ETX 90 has evidently risen about 10% over the last couple of months. I see itís commonly selling from the catalog retailers in the $325 - $330 range, which is still a tremendous bargain. A good quality 40mm eyepiece (very highly recommended) can be picked up at any of several places catering to amateur astronomy buffs. They run anywhere between $50 and $75. (Orion at www.telescope.com is a good place to check.) When you call them, tell them you want the eyepiece for a Meade 90mm ETX spotter. They may not be aware that the Weaver is the same thing with a different paint job. BTW, use the 26mm lens thatís supplied with the scope for viewing of the moon. The view is absolutely spectacular!!

     Bottom line - this spotter will provide you with the very best resolution on the market, for a total cost of only around $400. How do you beat that? You canít.

Good luck and good shooting, Todd

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Warning: All technical data mentioned, especially handloading, reflect the limited experience of individuals using specific tools, products, equipment and components under specific conditions and circumstances not necessarily reported in the article or on this web site and over which IHMSA, The Los Angeles Silhouette Club (LASC), this web site or the author has no control. The above has no control over the condition of your firearms or your methods, components, tools, techniques or circumstances and disclaims all and any responsibility for any person using any data mentioned. Always consult recognized reloading manuals.