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Old December 26, 2017, 11:01 AM   #1
ndking1126
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I know side focus distances are normally not accurate, but

I know side focus distances are normally not accurate, but I'm curious how far off yours are?

I have a Vortex Diamondback HP (decent scope I guess) and finally took the time to figure out what number on the side focus dial would correlate with actual distances. So I got out my laser range finder, bipod, a few boxes and found some items I could test it on.

With the rifle completely supported and me not touching it, I found out the scope had no parallax (reticle didn't move on the target as I moved my head) at the following:
-Actual distance of 60 yards I had to put the sidefocus knob on 105 (best approximation)
-Actual distance of 100 yards I had to put the sidefocus knob on 365 (best approximation)
-Actual distance of 130 yards I had to put the sidefocus knob on 490 (best approximation)

I was surprised the numbers were off that far. I even went back and did the tests again another day just to validate the numbers. Any concern this is too far off and should be looked at by Vortex? Thanks!
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Old December 26, 2017, 12:32 PM   #2
NoSecondBest
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Is the "side focus" a knob to focus the scope or is it a knob to set parallax distance? Most of my scopes have the actual focus on the rear of the scope and the other adjustment is to set distance for parallax.
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Old December 27, 2017, 08:48 AM   #3
ndking1126
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On my scope, it mainly affects parallax, but also adjusts actual focus some. If I'm looking at a target 150 yards away and adjust the knob to around 50 yards (ie, way too low), it will get a little blurry. If the side focus knob is at least reasonably close to the correct distance, the picture remains pretty close to in focus.

From everything I've read, this is how the side focus will work on basically all scopes, but I only have experience with this one.
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Old December 27, 2017, 09:39 AM   #4
NoSecondBest
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With all due respect, I think part of the problem may be your eyes. If your scope isn't focused correctly then the parallax knob will allow some apparent focus adjustment. Have you gone through the process of focusing your scopes crosshairs by looking up at the sky as you adjust clarity? Most all decent quality scopes with parallax adjustment are pretty near perfect at the indicated distances marked out on the scope. It's the human part of the process that kind of gets in the way. Have you had your vision checked recently? It sneaks up on you without realizing it's happening and it doesn't take much change to be noticed in cases like this.
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Old December 27, 2017, 11:23 AM   #5
ndking1126
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NoSecondBest, I have had my eyes checked recently and they are good to go. Also, I did adjust the crosshairs by quickly looking into the scope at the sky and adjusting the eye piece closest to my eye. Good thoughts, thank you for offering them as a suggestion.

Initially when I was playing with the side focus around the 100-200 yard settings, it wasn't very clear and I was a little disappointed in the optical clarity. After finding the correct numbers to equate to the actual distance I was looking at, I find the overall clarity to be better than I've ever seen with this scope. So that's a plus.

Quote:
If your scope isn't focused correctly then the parallax knob will allow some apparent focus adjustment....Most all decent quality scopes with parallax adjustment are pretty near perfect at the indicated distances marked out on the scope
Vortex's owner's manual says "Turn the side focus knob until the target image is as sharp as possible." To me this indicates the side focus knob can affect the overall focus of the scope. I've done a lot of reading on forums and by far, from what I've read, the consensus is the opposite of what you are saying here - not that I accept them as gospel fact, but overwhelmingly I've read that you can expect the side focus to factor into the focus and that the numbers on the knob aren't likely accurate. I'd be interested to know how you came to these conclusions.
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Old December 27, 2017, 02:46 PM   #6
NoSecondBest
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Quote:
I'd be interested to know how you came to these conclusions.
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Just from owning dozens of high quality scopes over the last 50+ years of shooting both competition and hunting. I'm only offering my experiences and I'm not trying to take on everyone on internet forums. I've owned a couple of scopes over the years that were lacking in this regard, but all of them were low end scopes owned back in the day when I couldn't buy the better ones. Most notibly were the Tasco World Class, and some low end (very low end) intro models produced by some large scope manufacturers. I'm not saying you have to spend a grand to get a good scope, but I will say you don't get the best for a couple of hundred. Most of mine now days are the better Leupolds. I think they give the best overall value for dollar spent. Good luck getting this sorted out.
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Old December 27, 2017, 03:27 PM   #7
444
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I have dabbled in air rifle field target matches.
In these matches, the targets are at various ranges from as close as maybe 5-7 yards to as far as maybe 50 or 60 yards.

Obviously, range estimation is critical with an air rifle.

The only thing you are allowed to use for range estimation is your scope. You use your side focus for range estimation.

So, I think it is common practice to do bascially what you are doing now, except the people I know (as well as myself) added a big wheel to the side focus adjustment knob: mine is about 5" in diameter. I then put masking tape over the scale on the knob and put marks (using a Sharpie) onto the tape to accurately correspond to the range.

To actually answer your question: most of scales on my scope are not very close to where they actually focus for me.

One thing you might want to try is to put a target at a known range. Then set the side focus knob to that known distance on the scale. Then adjust the focus knob on the rear eye piece to make it as clear as possible. I have found that this helps a lot. In other words, when you focus the scope, do so at a known distance with the scope's side focus set to that distance.
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You know the rest. In the books you have read
How the British Regulars fired and fled,
How the farmers gave them ball for ball,
From behind each fence and farmyard wall,
Chasing the redcoats down the lane,
Then crossing the fields to emerge again
Under the trees at the turn of the road,
And only pausing to fire and load.

Last edited by 444; December 27, 2017 at 03:32 PM.
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Old December 28, 2017, 05:58 PM   #8
reynolds357
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Nowhere near accurate. Some of the more high end scopes don't even have numbers on the side focus knob. The side focus both focuses and adjusts parallel. The rear adjustment is for cross hair clarity adjustment.
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