I have a new FFP Vortex Viper PST 6-24x50mm sitting on a 20 MOA base. A 100 yard zero has the elevation nearly bottomed out. If I set the mag ring to 6x, the field of view is partially obscured like its offset. I ran the elevation to the top end extreme and the field of view was offset in the opposite direction. In the middle of the elevation range, the field of view is centered. Is this normal or do I have a malfunctioning scope?
Rifle Scopes Field of view is offset at extreme ends of elevation adjustment... Normal?
- Thread starter Sgt_Jamez
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I have the exact same glass on a 20moa base, and haven't seen what you're describing. Does adjusting your cheek weld position forward or backward (changing eye relief) help or make it worse?
Yes what you are describing is in fact normal. From what I remember vortex telling me is that in the extreme limits of adjustment you are seeing the inside of the tube. Almost causing a oval shape rather than circular.
Fell free to call vortex customer service but I'm fairly certain that's the explanation I was given when I asked last year.
-chris
Fell free to call vortex customer service but I'm fairly certain that's the explanation I was given when I asked last year.
-chris
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That is normal. The erector inside the scope is moving up and down, and when it is at the extreme limits of travel is actually viewing through the edges of the objective rather than the center of the objective, and therefore the view can be distorted. Disregard the text in these picture as it's incorrect. When you move your elevation turret 'up' your erector tube moves down, and when you move your elevation turret 'down' the erector moves up. The ways of 'fixing' this are, changing the base, making the scope's objective larger or closer to the erector tube. I would suggest swapping your 20 MOA base for 0 MOA, and see if it helps in regard to the 6x at 100 yards.
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No, the text is correct, see explanation here: http://www.snipershide.com/shooting...-reticle-travel-within-scope.html#post2470771
I stand by what I said. The Erector moves downward to increase elevation adjustment, and upward to lower elevation adjustment. When the erector moves downward, as does the image plane, to compensate one must rotate the entire optics platform, IE rifle, upwards in order to compensate for the offset of the adjustment. With the rifle barrel moving upwards indirectly proportionate to the erector system this allows the trajectory of the projectile to reach a higher elevation in regards to the sighting plane. This is the same concept whether you are using iron sights or a rifle scope, and even your base. This is the reason why scope bases are angled DOWNWARD toward the muzzle. This allows the scope to be zeroed closer to the upper limit of travel for the erector system which gives you more downward movement of the erector system, which allows you to reach longer ranges.
This is the best image I could find without drawing my own. The red line represents the erector, or the image plane, and the blue line represents the trajectory of the projectile. If one moves the erector closer, IE downward, to the rifle bore, the trajectory of the bullet rises. If one moves the erector farther from the rifle bore, then the trajectory of the bullet is actually lower.
For this reason I believe the OP has too much 'downward' cant, and therefore if he were to swap his 20 MOA base for a 0 MOA base, he would get rid of his optical distortion at lower magnification at close range.
This is the best image I could find without drawing my own. The red line represents the erector, or the image plane, and the blue line represents the trajectory of the projectile. If one moves the erector closer, IE downward, to the rifle bore, the trajectory of the bullet rises. If one moves the erector farther from the rifle bore, then the trajectory of the bullet is actually lower.
For this reason I believe the OP has too much 'downward' cant, and therefore if he were to swap his 20 MOA base for a 0 MOA base, he would get rid of his optical distortion at lower magnification at close range.
No it is not, for the reason I explained in the linked post. The erector "looks" at an image that is upside down (the image created by the objective system in the first focal plane), that's why it has to move counter to what intuition tells you. I understand your puzzlement, because I used to think the same way before I actually got in contact with scope mechanics. If I still thought so, I would have been fired long ago.
You could also achieve the adjustment by tilting the whole scope, like has been done with those old Unertls with external adjustment, and then the scope would indeed have to be tilted downward in order to adjust for long range, but that's not what happens in a modern scope with a moving erector.
If you don't believe me, just look into the objective of a scope (high power/long objective focal length and big adjustment range is easiest to see) while dialing up/down and see for yourself.
In regards to Ballistics post. No, actually your statement is incorrect. The text in the diagram is correct.
The image enters the erector system inverted at the first focal plane, or the first point of convergence which requires your erector to move up to raise your point of impact. By raising your erector up your point of AIM is lowered to compensate for the elevation correction.
Top is bottom and left is right in an image erecting system.
The image enters the erector system inverted at the first focal plane, or the first point of convergence which requires your erector to move up to raise your point of impact. By raising your erector up your point of AIM is lowered to compensate for the elevation correction.
Top is bottom and left is right in an image erecting system.
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Scopes with a limited amount of internal travel require less cant on the base. For example if a scope only has 50 MOA total internal travel and was mounted on a 20 MOA rail nearly all of its downward travel has been used to compensate for this. At this point the erector is nearly bottomed out as well as the erector spring to obtain a zero. You will achieve more elevation correction but it will come at a price and that is usually a lack of image quality. Once the erectors position gets closer to center the image will noticeably improve and the shadowing on the edges will disappear.
