|
I was blown away at last
year’s Shot Show when I saw a prototype of a new 90mm spotting scope from
Weaver - the ETX. It looked identical to Meade’s 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 wasn’t 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 Meade’s dark blue. It was also one of the most impressive anodizing
jobs I’ve ever seen. That green scope tube looked like it had a couple of
layers of clear coat on it. I know it didn’t, 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 couldn’t help but blurting
out “This is one fantastic bargain.” 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 competition’s hair turn gray. As it turned out, I was
absolutely right.
So what is a catadioptric
telescope? It’s 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 “folded” 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. (I’m
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 1250mm’s (48.75 inches) while the overall length of
the tube is only 11 inches.
So how does the ETX’s 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 isn’t
going to mess up that pristine image that’s 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 it’s 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 what’s that supposed to mean? As a hypothetical example, if you have
a mirror with a surface that’s 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 Meade’s 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 we’re
accustomed to working with. First of all, this isn’t a sealed, nitrogen
filled, shock proof, water proofed, rubber armored product. As such, and
because of it’s size, it’s not really suitable for being taken into the
field on a hunt. However, the lack of those characteristics doesn’t
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 you’re 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 Weaver’s out to the range and started to put it through it’s 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 couldn’t get the whole animal into
the image. Well this wouldn’t do.
I then got an inspiration. I
own a Meade 8” 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
Mike’s range bag. This lens produces around 30X of magnification versus the
26mm’s 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 30mm’s of eye relief. (On some other spotting scopes, you’ll get only
somewhere between 7 and 12 mm’s of eye relief.) The 40mm lens made all the
difference in the world in the scope’s performance. When pointed at the 200
meter ram targets, around two and a quarter animals presented themselves in
the 40mm’s eyepiece which is more than wide enough. Even when pointed at the
chicken, the whole animal and at least 6” 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 I’ve ever seen in any spotting scope - no matter what the cost, and I
don’t say this lightly. As you know, I’ve 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 I’ve 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 Club’s 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 club’s 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 3’ 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. I’ve 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 it’s coupled with outstanding performance.
The price of the ETX 90 has
evidently risen about 10% over the last couple of months. I see it’s 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 that’s 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 can’t.
|
