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Riflescope primer (diagram added) Login/Join 
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A quick update after day 1 of SHOT 2019.

I've not seen anything but the inside of the March booth today and I have been playing with the newest scopes from March:

The 6-60X56 Genesis with 350MOA (100mil) of up elevation and 50MOA (14mil) od down elevation. The windage has a range of 150MOA (43mil).

The 4-40X52 Genesis with 250MOA of up and 50MOA of down.

The 5-42X56 with 140MOA (40mil) of adjustment range, super-ED lenses, 50MOA of adjustment per revolution and wide-angle eyepiece (26degrees) to increase the eyebox size.

I'll have pictures and more to say about those later this week. The three scopes are all FFP.

This message has been edited. Last edited by: NikonUser,
 
Posts: 2832 | Location: Texas | Registered: June 20, 2012Reply With QuoteReport This Post
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Here are some pictures from SHOT 2019. I'll come back to discuss the scopes.

http://img.gg/BWiVJ9X
 
Posts: 2832 | Location: Texas | Registered: June 20, 2012Reply With QuoteReport This Post
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I didn't have much time to visit any other booth at SHOT, except for the Sig Sauer booth.

I did talk to lots of people who came to the March booth and they, of course, would tell us about any other new thing in optics at various booths. That phenomenon works both ways, of course, and because of the Genesis and the new 5-42X56 FFP scope, we got visited by many competitors. Leupold sent two groups of people to visit our booth and they spend quite some time looking at the scopes and playing with them. It's not an issue because they have nothing approaching the March scopes in terms of capabilities and prices, so there's really no competition. Nikon also came in force and spent quite a bit of time at the booth and they even asked questions. Again, there is no overlap there either. I was happy to see Nikon folks as I have lots of Nikon photographic equipment (hence my screen name here,) and a few of their scopes.

The upshot of this is that in strictly optical riflescopes, the three that I listed above represent the state of the art currently, which is why we were visited but did not reciprocate. There are digital scopes coming out and that will continue to expand, but ultimately you still need decent optics to capture the image.

Let me explain why and how this relates to existing scopes and in the future, digital optics. In a riflescope, the portion between the turrets and the objective lens is what sets the tone, so to speak, for the whole riflescope. When I was looking at the 5-42X56, I was struck by two things: 1- the distance that I just mentioned was much shorter than in the 5-40X56 scope and 2- the adjustment range is about double what you usually have in a 30mm scope. There is a relationship between the two observations.

As I described in the OP of this thread, the distance between the objective lens and the turrets actually represents the first focal plane setup. The distance between the objective lens and the turrets is the basic focal length of the scope. The significance of the turrets is simple; that's where the inner tube ends and the reticle of the FFP is located. If you have a longer focal length, you have more magnification, and less field of view; conversely if you have a shorter focal length you have less magnification and a greater field of view. With me so far?

The focal plane is not a dot, it's actually a circular plane, and in this case it is 30mm in diameter, the inner dimension of the riflescope main tube. By using a shorter focal length than usual, we get a larger field of view, albeit with smaller details. After all you can only have so much on the focal plane, right?

Now, I hear what you are saying, “NikonUser, if we have smaller details, that means we need more magnification somewhere else, right?” To which I answer, “I should think so.” This also means that your glass must be absolutely superb if you’re going to depend on a smaller image in the first focal plane, which you will magnify more later on. It is a testament to the glass on this riflescope that it has such great clarity and resolution so that even starting with a smaller image at FFP, we get a great view at the eyepiece.

Now by virtue of having a smaller image at the FFP, this means the movement of the inner tube represents a greater displacement compared to the same movement on a larger image. This is how you get a 140MOA adjustment range without shrinking the inner tube and its lenses or expanding the main tube to 40mm or more.

Also, you must match the reticle to this different focal length which is why existing reticles do not fit this riflescope and new ones have to be designed. Of course, you can have the exact same design as that of an existing reticle, but it must be recalculated for the new focal length as they are not interchangeable, or anything beyond a dot or dot/wires or something similar that does not depend on any scaling.

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Posts: 2832 | Location: Texas | Registered: June 20, 2012Reply With QuoteReport This Post
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Thanks,NikonUser, for all that, and especially your explanations. Excellent information.




“Without its tough spearmen, Hellenic culture would have had nothing to give the world. It would not have lasted long enough. When Greek culture became so sophisticated that its common men would no longer fight to the death, as at Thermopylae, but became devious and clever, a horde of Roman farm boys overran them.”
— T. R. Fehrenbach, This Kind of War
 
Posts: 39105 | Location: 10,150 Feet Above Sea Level in Colorado | Registered: April 04, 2002Reply With QuoteReport This Post
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Here is a first quick diagram that I put together to help illustrate some of the things we're talking about here. It's not to scale, but I'm hoping it's not too misshapen either.

This diagram illustrates the front portion of a variable magnification riflescope. My goal here is only to illustrate various parts and how they work together, this is NOT representative of any riflescope and the exact location of the parts is not definitive; this is just to convey the concept.

In a side focus scope, that focus lens you see between the objective and the FFP moves back and forth and is controlled by the side-focus knob. What this lens does is to focus the objective onto the FFP depending on the distance from the scope to the objective. In an Adjustable Objective scope, elements of the objective lens group itself are moved to adjust the focus and so there is no Focus lens between the objective lens group and the FFP. An AO is simpler, easier to build and is better optically that a side focus, but it's more inconvenient to use.

As I try to illustrate the FFP is where the image from the objective is projected and focused. The image is the size of the inner diameter of the main tube, or 26 millimeter in the case of a 30 or 34mm tube. The FFP reticle will be at the end of the inner tube, right in the plane of the first focus. This reticle can be a simple as a crosshair or even a dot, etched on the glass or as complicated as Horus or Christmas tree arrangement. The etching has to be extremely precise and as you can guess the dimensions of the reticle objects must be maintained with the focal length of that first part in order to be meaningful in the case of anything more complex than a crosshair or a dot. Actually even those simple reticles must have their dimensions just so in order to represent some size relation with the objective. This is where we see the specs that the dot is 3/32nd or 1/8 MOA, etc.

The image at the FFP is going to be magnified according to the focal length of that first part. It's not a big magnification , more like in the order of a couple of Xs depending on the diameter of the objective and the distance between that objective and the FFP (also known as focal length) but it's some magnification. So the reticle dimensions must match the focal length here in order for the reticle to be useful in ranging and so on.

That inner with the reticle at the front, contains the erector assembly that flips the image right side up and side to side and, in the case of a variable, the zoom lenses that will move back and forth to increase or decrease the magnification. The inner tube will have an OD that is smaller than the 26mm of the ID of the inner tube and that's where you get adjustment range. In a 1 inch scope, (25.2mm OD), the inside diameter of the main tube will be closer to 21.2mm instead of 26mm for the 30/34mm tubes. That extra 4.8mm of travel is what gives the extra adjustment travel in the 30/34mm tubes.

So the inner tube goes up and down, left and right with respect to the stationary image projected by the objective in the first focal plane. When you twist the knobs you're simply moving the inner tube to look at a different place on the FFP. The field of view that you get at the reticle is dictated by the inside diameter of the inner tube and the magnification after the FFP.

Anyway, this is a very basic diagram and it's not an exact representation of the afocal device called the riflescope, but I'm hoping it helps the reader understand a little more.

http://img.gg/s2cul9Y
(Just toggle the arrow to see the other picture.)

I don't seem to have html markup capabilities, otherwise I would include the image right here. This forum software is a little ancient, but it is very fast and stable.

This message has been edited. Last edited by: NikonUser,
 
Posts: 2832 | Location: Texas | Registered: June 20, 2012Reply With QuoteReport This Post
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Here is the rest of the diagram.

In here, we see the zoom assembly and the location of the so-called Second Focal Plane. Irrespective of the design of your scope, there are First Focal and "Second" Focal planes in all of them; the SFP or FFP designations only indicate the location of the reticle. After the second focal plane you have the eyepiece assembly, which is an ingenious piece of optics in its own right. I has magnification and diopter adjustment built-in.

You get more of an appreciation of the eyepiece assembly when you look at a spotting scope with interchangeable eyepieces such as my Kowa. I have two eyepieces for that optic, a Long Eye Relief 27X eyepiece and a 20-60X eyepiece. The LER eyepiece allows the eye to be further away from the eyepiece and still get a clear and complete picture. These eyepieces are expensive and little jewels of optics in their own right. And heavy too. Since there is not a reticle on which the spotting scope optics needs to be properly focused, these optics do not have a diopter adjustment, unlike riflescopes.

http://img.gg/s2cul9Y

(Just toggle the arrow to see the other picture.)
 
Posts: 2832 | Location: Texas | Registered: June 20, 2012Reply With QuoteReport This Post
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quote:
Originally posted by sigfreund:
Thanks,NikonUser, for all that, and especially your explanations. Excellent information.


I missed your post earlier. Thanks for the nice comments, I appreciate that.
 
Posts: 2832 | Location: Texas | Registered: June 20, 2012Reply With QuoteReport This Post
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