# The effects of moving the scope forward or back



## macnimation (Nov 30, 2010)

Hi,

I could not find any discussion on this topic in the forum so apologies if I missed something.

My indoor Bow is tuned perfectly and apart of human error, my X7 will hit the 10 ring 8/10 times, which is great for me.

At the weekend, I decided to extend my scope out further as I use the Sureloc Supreme 550 and I had it set to about half of the length. I extended it to the second last notch.

Shooting again I found my arrows were hitting low ( 9 liners )directly at 6 o clock. I put the scope back again to the original position at I started hitting the 10 ring again.

Is this normal, as I would not expect this to happen. If the bow is set up correctly surely the scope should shoot the same no matter how far out it goes?


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## giltyone (Nov 9, 2009)

Moving the scope forward makes your sight tape spread out (covers a bigger angle of view) - moving it towards the peep shortens the tape.

If you use a sight tape program like OnTarget2! - you need to know distance from sight/scope to peep to get an accurate sight tape.


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## klemsontigers7 (Jul 1, 2008)

Moving it forward moves it on a slightly different axis than your line of site. It moves it perfectly dead directly away from the bow, where your line of site (from your eye to your pin) is not perfectly dead directly away from the bow. I don't feel like drawing this up in Solidworks... so paint will have to do.

Dimensions are EXAGGERATED in the drawing

Yes, I know it's ugly but here is what is going on. The round thing on the left is your eyeball. The arrows are your pin in it's before and after positions. 
As you can see, your line of sight is actually at a down angle going to the target.
The two long black lines are your line of sight, the bottom one is before, the top one is after. 
As you can see, your line of sight goes up, making your arrow to appear to be lower than your line of sight.

It's just physics, nothing wrong with your bow.








The points of the two arrows that I drew (to represent your pin) are in line with each other with respect to the bow.


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## klemsontigers7 (Jul 1, 2008)

To help exaggerate the point even more, imagine how low your pin would have to be if it were 20 yds away, at the target. This is why you are shooting low when moving the pin toward the target.

Also, as mentioned above, pin gaps increase when moving the pin toward the target. Again, imagine how big the gaps would be if the pins were all the way at the target, vs how small they would be if they were all the way at your eye.


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## klemsontigers7 (Jul 1, 2008)

Okay, no comment? I assume you understood.


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## macnimation (Nov 30, 2010)

Sorry, I was away travelling and could not respond.

Thanks for the responses it makes sense.

My indoor bow is set only to shoot 18m and wont change from that distance. I was just thinking there might have been a tuning issue.

Again, thanks for the explanation.


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## ron w (Jan 5, 2013)

it also changes the acuity of your magnification as a system. you can move it in or out to produce a sharp or blurry picture of the target. some shooters prefer a slightly fuzzy picture of the bulls eye for 5-spot shooting because it hides all the holes that aren't in the center, so they don't look at them as they are aiming......and some guys like the picture to be crystal clear and sharp. you do this by moving your sight bar in or out and finding the setting that gives you the picture you prefer to see.
of course, as said, moving it in or out will also change the POI., so a small elevation change may have to accompany a focus adjustment.


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