A while back I saw a video where someone locked their rifle down on a target and videoed through the scope all day and as the sun came up and crossed the sky, the target seemed to move. Anyone have a link to that video?
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Range Report Sun angle makes target move?
- Thread starter veezer
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I think that was about sun heating the scope and causing shift due to expansion of tube. I want to say I saw it on the shooting times webpage.
I don't know what video you're asking about but I witnessed this over the last 2 outings shooting. Two weeks ago I had perfect conditons to shoot ELR. Overcast with light winds. I set up and gathered dope. Then last weekend I returned to the same spot and shot again only it was sunny, almost 20* warmer and the wind was blowing from 4-8mph. This time I had to dial in another 1/2-3/4 moa to hit in addition to the wind. Given the increase in temp alone I should have had to dial down .5 moa.
This is quite common and has nothing to do with heating the scope , in short range BR and other precision shooting they look for this as it changes the picture quite rapidly with sunny weather and for example some cluds , picture moves up and down when cluds block the sun .
D
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For what it's worth, I have taken a spotting scope with a reticle in it and watched the target across the valley on a partly cloudy day . The sun was almost directly overhead. The target moved up and down 1+ MOA against the reticle as the sun moved in and out of the clouds.
After about 30 cycles of this happening over the course of a couple of hours, I had no doubts about the reality or the magnitude of the effect.
After about 30 cycles of this happening over the course of a couple of hours, I had no doubts about the reality or the magnitude of the effect.
"Light's up, sights up..."
This has been a long time mantra among Highpower shooters.
As it goes, one adds 1MOA of up adjustment to sights when the sun's light goes from overcast to bright sunlight.
The reasoning is that this is because the lighting difference produces the equivalent of an optical illusion to the sight picture. It's believed to be a vision trick related to contrast and resolution.
Greg
This has been a long time mantra among Highpower shooters.
As it goes, one adds 1MOA of up adjustment to sights when the sun's light goes from overcast to bright sunlight.
The reasoning is that this is because the lighting difference produces the equivalent of an optical illusion to the sight picture. It's believed to be a vision trick related to contrast and resolution.
Greg
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D
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That all depends on the angle and intensity of the mirage and the conditions at zeroing.
I've been noticing and recording this effect for a few years now. What I have seen, is that strong sun is worth pretty close to 1 MOA of change at all ranges. That being measured from a zero established in a light neutral (heavy overcast) condition. If your zero was established in any other light condition, then it will be some fraction of that.
Mirage will either cancel this effect or add to it, depending on which way it runs. The worst mirage I have been able to quantify is 1.5 MOA. That was heavy mirage blowing left to right, with some 3-4 mph winds. This was observed at a PR1 class at Sac Valley on a square range @ just 200 yards. Rifles were zero'd in the morning with no mirage, sun was behind and at about 4:30 clock direction. At the end of the class, all participants shot zero again. This time with sun to the 9 o'clock and very strong with heavy mirage and the mentioned light winds. The average zero shift among the entire class was just under 2.25 MOA!!
Light's up, sights up.
It's a damned shame that more people don't ever learn to use irons well. It's not that you'd always want to, but some of the lessons learned are really useful to optical shooting, and some are learned better than when you can stare at your bullet holes.
It's a damned shame that more people don't ever learn to use irons well. It's not that you'd always want to, but some of the lessons learned are really useful to optical shooting, and some are learned better than when you can stare at your bullet holes.
D
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Lights up, sights up is a truism, but an extreme simplification. The reason we can get into the weeds about this stuff is because we can actually see the results well enough to discern even small differences in real time.
I shot irons for all of my youth. I was 27 before I ever owned a scope. At 47, I no longer have the eyesight to shoot as well as I once did unmagnified.
Well sure it is, but my statement about lessons is still true.
I did the opposite of you, learning (well. REALLY learning.) irons later in life.
I actually ignore/ignored the idiom I quoted because I shoot center hold, same as scoped shooters.
So what if you just keep aiming at the middle of the target image? Do you not get centered hits in the afternoon?
In the weeds indeed.
The only time I've noticed any significant apparent shift due to light using metallic/iron sights is with a front post as the bull can wash out or the white space can trick your eyes depending on what sight picture you are using (6 vs CoM vs flat tire vs LoW vs target frame vs ??). I don't really notice anything with front and rear apertures, but my eyes are pretty good and I keep my eye centered pretty well. And to be honest, with a 6 oclock hold I tend to shoot high when the sun is bright so I usually switch to line of white or CoM.
When your parallax setting is not dialed in, and you move your head around, is the reticle moving in relation to the target or target moving in relation to the reticle? Or is it really just how the scope is projecting the image of both the reticle and target at your eye? What about when the parallax setting is dialed in perfectly? Why does nothing move?
My guess is that in that video, the parallax was not dialed right.
When your parallax setting is not dialed in, and you move your head around, is the reticle moving in relation to the target or target moving in relation to the reticle? Or is it really just how the scope is projecting the image of both the reticle and target at your eye? What about when the parallax setting is dialed in perfectly? Why does nothing move?
My guess is that in that video, the parallax was not dialed right.
D
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On most data books target pages there is a specific section concerning the sun position/or absence.
After logging data a pattern as mentioned forms.
R
After logging data a pattern as mentioned forms.
R
I just watched the video and read all the above discussion about sunny vs overcast. The video does not seem to demonstrate a change of sight picture with sudden light changes from clouds moving in front of the sun. There are several frames of the video that show overcast conditions and the sight picture did not change drastically. It does appear to be something like a scope heating up gradually and shifting internals.
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