Changing Zero

[Innocent]

Kyle,
Excellent job with your photos and drawing.

Mary

[Jason]

At our range we don't walk around to random locations to shoot from, giving us random angles on random animals.
...
Seriously, light is such a non-issue it's not even funny. And the fact that you guys keep trying to argue it is even more strange.

Whether you accept it or not, the sun does change positions during the day and the light coming from it does reflect off the targets differently as it changes position. My example did not include the targets or shooters changing position, and I suspect Kyle's example that included it was only to try to demonstrate the principle, not the exact situation, that I was describing.

The fact that you are dismissing the opinions of very experienced shooters and, more importantly, some of the best spotters in the sport is what seems strange to me.

[steve b.]

I was wondering (yikes) if we could set up at dusk / dark, a rifle in a rest, pointed at a target, like the Turkey, and take a powerful flashlight and imitate the suns movements across the target and see if the image changes in the scope? Would something like this work, or did I pick the wrong week to stop sniffin' glue?

s.

[deadeyeky]

Kyle,
Excellent job with your photos and drawing.

Mary

thank you mary, it gave me a chance to fool around with my dads new camera,

yes i was trying to demonstrate jasons statement,

now, with mirage, LIGHT itslef has everything to do with how we see the target, when we see something through our eyes, we see the light reflecting off the object, and when heat rises, it twists, turns, bends light in many different ways, moving the image we see, and not the object itself.

again like i said im my previous post, photos and drawings, angles and dimensions have been exagerated to show the effects, so shorty, tell me if you go to the designated chicken line to sight in, then move all of your gear and rifle down the line to pigs, then so on for turkeys and rams, i know i dont, and if you did not sight your rifle in at each designated position for each animal, then the distance will be a little farther, i would say 6 feet at the most at our range, but go to one with at least 5 banks of each animal, and that distance could be greater. and whatching guys here at the state sb benchrest championship here in gonzales, 6 ft makes a big difference. and im sure at least a few chickens, pigs and turkeys got turned just a little bit, a few degrees, (and im also pretty sure that you didnt walk down each line to make sure they werent turned) but it still makes a big difference when every variable comes into play,

different amounts, and the direction of light does make the animals look different, the surface we shoot at on the animal is not perfectly smooth, and the paint is not applied perfectly every time, when light hits a textured surface at different angles, the shades of light we see reflected off the animal are different. now i know that when the animals more or less blend in with the berm behind them they look smaller, and if say the animals are paint white, with real dark berm behind, then they stand out and look bigger.

[_Shorty]

I'm now wondering if I can get one of my cameras to take a decent picture through my scope...

I was wondering (yikes) if we could set up at dusk / dark, a rifle in a rest, pointed at a target, like the Turkey, and take a powerful flashlight and imitate the suns movements across the target and see if the image changes in the scope? Would something like this work, or did I pick the wrong week to stop sniffin' glue?

s.

[steve b.]

I was reading this info, and I wanted to share the link and see what you all thought.

http://en.wikipedia.org/wiki/Air_density

Also, take a look at the chart under the heading: Importance of temperature.

I noticed that the speed of sound changes considerable with the change in temp. This would impact the bullet's velocity.

Ideas?

[deadeyeky]

wow, great find, i need to look at wikipedia more....

well theres another reason why hotter temps make bullets go higher, along with making the air less dense, higher temperatures also generally make the air more humid depending on the vegetation and stuff around, which makes the air even more less dense, hmmm i thought humidity makes air more dense, wikipedia really knows it all

[Innocent]

Kyle,
Not contesting what has been posted on the link to Wiki....not having had time to read it yet (in transit to Benton) but use caution in trusting all things printed/posted. Keep doing what you have already shown in the photograhs, try it yourself and see what happens. And most of all never stop observing what others do and how well they achieve success in all things. Silhouette shooting is a demanding and tough sport, but it can teach you a lot about your own self, and the environment around you, not to mention the social harrassment that we dish out to each other.

Keep up the good shooting and learning this great sport.

Mary

[steve b.]

Kyle,

I double checked some basics that Wiki suggested, and it is correct on the physics is lays out. Gas laws and general thermodynamics support this link, or rather, this link is just a basic discussion of some principals to the gas laws, ect.

think of the weight of water, and then think of the weight of dry air, in terms of basic mole weights ( yep, chemistry class again), and it makes sense.

Here is another interesting quote:

"Humid air is less dense than dry air because a molecule of water is less dense than molecules of nitrogen and oxygen. Isaac Newton discovered this phenomenon and wrote about it in his book Opticks.[1] Avogadro's ideal gas law states that a fixed volume of gas at a given temperature and pressure always contains the same number of molecules regardless of what type of gas it is. Consider a cubic meter of dry air. About 78% of the molecules are nitrogen (N2), with a molecular weight of 28. Another 21% of the molecules are oxygen (O2), with a molecular weight of 32. The final 1% is a mixture of other gases. Combining these weights in the correct proportions gives an average molecular weight for air of about 29. If molecules of water vapor (H2O), of molecular weight 18, replace the diatomic nitrogen or oxygen molecules in this fixed volume then the weight of the air decreases, and hence the density decreases. Thus, humid air has a lower density than dry air at a specified temperature and pressure."

anyhow, i thought this would be neat to look at in that I think it helps add info to the discussion.

s.

[dryfire]

Found this discussion intriguing ! I consulted the omniscient Google about
"bending light rays" !
It appears that light is bent as it passes through changing mediums - ie less dense to more dense air or a more graphic example from air to water. Changing atmospheric conditions then would cause an apparent shift in the position of an object , eg a silhouette target even as close as 40m.
And,except for light passing near a celestial body with an extremely powerful magnetic field which may influence the path of light it appears light otherwise follows a straight path.
Any apparent change in the position of an object would then be attributed to changing atmospheric conditions, temperature,humidity, movement,density.

Objects may appear to vary in size or distance relative to the amount of reflected light but it appears that if the medium that the light passes through from the object does not change then the light's path does not change - hence no image shift.

[jneihouse]

No to pat myself on the back or anything, but I'll say it again.....Can I keep a dead thread going or what?

In all seriousness though, lost of good stuff here.

Kitty

[dryfire]

Even though an individual may be less experienced in the specific subject matter - silhouette shooting and spotting they may have a very clear understanding of the physical principles involved and shouldn't necessarily be branded as a heretic.
Straight shooting to all !

[Bob259]

No to pat myself on the back or anything, but I'll say it again.....Can I keep a dead thread going or what?

In all seriousness though, lost of good stuff here.

Kitty

You've done well Commander Kitty

[Kevin6q]

The example of the transit was interesting. Can a scoped rifle be set into a rest and aimed in the AM. Each hour the POA is noted and a round fired w/o touching the rifle. Does the POI change? Does the POA change? Do they change the same amount/direction?

I'd try this myself since I have a 50 meter range at home but no scoped rifles or rests.

If the change in POA is caused by diffraction due to changes in air density does this density change also affect the POI?

As light moves through a density change it bends. The greater the delta, the greater the bend. A good example is looking at a fish. When you are in a boat (on a dock or whatever you prefer) and the fish in underwater, where we see it is not where it is. The density difference between air and water is huge; about 1,000 times more dense for the water. Even with a great temperature differential the air change will be orders of magnitude less.

The fish example is also one density change and on the range there might be thousands of changes in air densities over 50 to 100 meters, bending the light all over the place.

Assuming the change of air density is uniform, the POA should not change since it is the density differential that bends the light moving the perception of where the target is. With a uniform density change, how much will the POI move?

[Jim Beckley]

This post has been fun to look at and even informative, but as I look at the names who have shot a 40/40, Kurreck, Lawton, O'Neil, Sanchez, Winstead-Severin, and Perry (SB Standard Rifle), I wonder if any of this BS crossed their minds while on their way to 40, somehow I doubt it!