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Adjustable Objectives?

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Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: February/24/2008 at 19:38
DAVE44 View Drop Down
Optics Journeyman
Optics Journeyman

Joined: November/11/2004
Location: United States
Status: Offline
Points: 652
I know that scopes with adjustable objectives are designed to remove parralax at powers above 10 power and to focus the lenses for better resoloution at given distances. If I sight in a rifle at say 100 yrds and set the objective for that distance and then decide to change the AO to 300 yrds. will that change my point of impact at the one hundred yrd. distance? If Adjustable objectives cause you to change your initial sight in point of impact then Im not interested in them for regular deer hunting. Also, if I sight in my gun at 100yrds. at 4 power then change my power to say 10 power and shoot at 100yrds. will just the power change cause any significant impact point shift? If so, are first or second focal plane reticles better for no shifts in zero from power to power? Can someone tell me?
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: February/24/2008 at 19:52
Dale Clifford View Drop Down
Optics Jedi Knight
Optics Jedi Knight

Joined: July/04/2004
Location: United States
Status: Offline
Points: 5087
while you have two optical systems running at an angle to one another, the parallex error in say a 50 mm objective set a 100 m  and an off angle target view (non parallex adjustment) at either 50 or 150 mm would be a poi shift of about 6mm. -- not enough to worry about.
strictly speaking there will be a shift, but your gun/load combination will not be able to see it. the effects gain when distance is added, but the difference depends. After 600 yds the effect is seen if the gu;n and load are up to it. If the SD of your loads is under 25 fps (for example), you can observe it and play with it-- using the power selector ring to lift the poi.
the effectis more apparent the wider the zoom range. 1st. FP are liked because they do away with this, by the people who shoot unknown distances.  However in most cases, the situation of a normal shooter is more of a known distance at a fixed target range and sfp are more popular.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: March/01/2008 at 20:45
niles coyote View Drop Down
Optics Apprentice
Optics Apprentice

Joined: October/25/2007
Location: Michigan
Status: Offline
Points: 83
at 100 yards you are not going to notice any change of impact.
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