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Need help in understanding scope tracking |
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fourinone
Optics Apprentice Joined: January/14/2006 Location: United States Status: Offline Points: 169 |
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Posted: January/01/2008 at 20:13 |
Hi; With the erector being round, elevation adjustment contact point on top, windage adjustment contact point on the right side 90 degrees apart from the elevation, an opposing spring contacting aprox. 135 degrees from both the windage and elevation points. How can an adjustment be made in either the windage or elevation without having any effect on the other. In other words...as an example it seems to me that when an adjustment is made with the elevation the round erector tube would have to move up or down and therefore the windage contact point would be in a slightly different place on the erector tube. What am I missing here? How can the tracking on any scope be exactly straight up or down when making an elevation adjustment. Are all scopes off just a little when it comes to the tracking? Thanks to anyone who will take the time to explain this to me and others who may wonder the same.
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Dale Clifford
Optics Jedi Knight Joined: July/04/2004 Location: United States Status: Offline Points: 5087 |
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there are a least two types of spring mechanisms, the one you describe and one that uses two sets of springs at 90 degs. Since the springs cannot collapse flat, they either have a little tube to compress into or are sprial and collapse into themselves. The finger springs you are talking about are not on the better scopes, but the tension they provide is simply there to keep tension against the gimbel or adjustments. Regardless of the springs a scope has it can have repeatability problems and should be checked, if you use dial in, this feature is more important than glass quality. Another problem is that even though one dials in a known number of moa, clicks, or mils, the reticle may not be moving that much. say you dial in 100 moa with 25 clicks, but test it against a yard stick or something at 100 yds. and it is only giving 96. This is a common complaint against Mk4 leos. but in defense it must be said that most shooters aren't really concerned with this. and a lot of scopes that ordinarily exhibit this behavior would never be candidates for dial in. So answering your questions yes -- far more scopes have this problem than suspected.
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fourinone
Optics Apprentice Joined: January/14/2006 Location: United States Status: Offline Points: 169 |
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Thanks Dale for the responce. Though the root of my question is still lingering in my head.
So here goes another stab at what I'm after....lets say you we have one of the good scopes with two springs as described above. With the erector tube being round and just two solid contact points; "windage & elevation" How can any one adjustment allow the round erector to move in just one direction without allowing it to move slightly in the other direction?
For an example; take a glass or can and place on a flat surface, place the tip of one of your fingers on the right side at the base. Make contact just like the windage adjustment does at the 3 o'clock point of the glass. Now move the glass straight up and see that now the glass does not touch your finger. Ok now if you push the glass to your finger tip again like the springs would have you'll notice the glass had to move slightly to the right in order to make contact again.
My question is how does it do this in a scope without allowing this to happen??
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Dale Clifford
Optics Jedi Knight Joined: July/04/2004 Location: United States Status: Offline Points: 5087 |
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I think I understand, how can the pressure be constant on a continually changing radius? Unless the erector is built in a race it can't. Fortunately there isn't a lot of movement inside the scope, ie the erector so the maufacturers only have to deal with an arc subtension, (and this is a guess) of about 5 degrees. Some long range scopes with a lot of throw take this into account. USO's long range 58 mms have the gimbels and gearing outside the tube so the tube rides in a race and the extreme needed adjustments using your theory (and it is correct) more error would be "seen" in the system towards the end of the run out. -- so a manu. can use a combination of approaches, who will be using the scope, price range--- if the user needs accuracy in those end ad. they have to pay for it. One of the reasons such extremes in price.
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