Changing Zero

[Bob Mc Alice]

Innocent said:
You've seen my ability to pick up things with my feet, I certainly prefer to use my feet constructively, and not hurt them, and continue picking up coins or other objects with my toes.


Wow Mary......I'm impressed..... I been doing that chit since birth. Let's see you swing from branch to branch with those talented toes of yours.....I thought so.

[Bob259]

I hope this mean Chimp is back McAlice.....

[Bob Mc Alice]

Sorry 'bout that all. Like I said, he's just a friend of mine. I dont have any control over him. Bob259, he has never really left.

[Bob259]

Man we miss him....

[Innocent]

McAlice,
What flavor of beer do I need to bring with me to get the chimps memoirs flowing?

Bob259, I might need to take up a collection to get enough of juice down McAlice, after I loose the bets in AR.....I mean, you know, wouldn't want to cut BB's ego too much.
Innocent

[Bob259]

McAlice,
What flavor of beer do I need to bring with me to get the chimps memoirs flowing?

Bob259, I might need to take up a collection to get enough of juice down McAlice, after I loose the bets in AR.....I mean, you know, wouldn't want to cut BB's ego too much.
Innocent

LOL ..... Understand Mary, besides he is our token Democrat

[Jason]

All of which has absolutely nothing to do with where the sun is in the sky. Thanks for playing though!

If experience has nothing to do with it, then why do the master class shooters tend to have spotters, (usually very carefully selected) and adjust their sights and or POA during a match based on the condition calls of their spotter and their own instincts?

Shorty,

You'd be correct if the targets we shot were absolutely perfectly shaped, specifically with absolutely perfect 90 degree corners. Since they are not, the direct sunlight does indeed hit different areas around the edges depending on where the sun is coming from relative to the target. For an example, let's say the shooters are facing due north toward targets facing due south with the summer sun moving from the east horizon to the west horizon during the day. Very early in the day, the sunlight would be reflected off the flat front face of the target to a lesser extent and off the rounded right edge of the target (from the shooter's perspective) to a greater extent. Since no direct sunlight would be hitting the left rounded edge of the target, the other ambient light being reflected from that rounded edge would be much dimmer to the shooter's eye and that area wouldn't be calculated into the perceived area of the target by the brain. The brain's picture of the target would include the flat front face and the right side's rounded edge, giving the perception that the target is centered slightly to the right of where it really is. Similarly, when the sun is highest in the sky, it would look slightly higher than it really was. Again, just before the sun dropped below the horizon in the evening, the target would be perceived as being centered slightly to the left of where it really was. The amount of the perception different from actuality here would depend on the target and the power/resolution of the scope, of course, but should not ever be greater than 1/8 to 1/4" of an inch by my reasoning. The greater the power and resolution of the scope, the less the shooter's brain will have to "fill in" information that didn't come from the image of the distant object through the eye, which will result in less of a delta between perceived position and actual position.

This light different is a small variable by itself, but it has to be combined with velocity and flight differences due to temperature and wind, as well as perception difference due to mirage. It takes a very experienced shooter or spotter to be able to decode all of the variables to keep bullets going where they are supposed to. Since silhouette shooting is all offhand and works on the principle of trying to center the offhand group size to maximize bullet contact with the target, that 1/8" from light difference can be important. In our sport, the shooter doesn't have the reliable feedback of seeing the previous shot's hole in the paper. A shooter's perception of where the shot went, especially on a miss, is not always reliable. They will know where the dot was when the shot broke. That's not neccesarily where the bullet actually flew. Even though it's possible to see the mark on the target as it goes down some of the time, I've never seen a shooter who could see that every single time.

[jneihouse]

Just for reference purposes, heres a pic of Innocent Mary at Winnsboro in 2007 about to pick up the dime on the concrete below Ducky with those talented toes ....Just in case there were any doubters....

Kitty

[img][img]http://i14.photobucket.com/albums/a336/ ... ertoes.jpg[/img][/img]

[jneihouse]

You'll also note that the ambient light makes the dime look slightly off center of Ducky, when in fact it is perfectly centered..

Kitty

[Innocent]

Commander Kitty,
At least it isn't light from our solar simulator....down due to complications from silicon tri coatings causing a melt down on an aluminum eyepiece, oh boy what another set of variables.
Outdoor ambient light, so much better.

Innocent

[jneihouse]

There is actually a touch of fill flash in there to keep the sunlight from the backside from darkening the picture....Flash was the same basic "warmth" as the sunlight though.....Nikon is pretty good at imitating sunlight...

Kitty

[Innocent]

.....Nikon is pretty good at imitating sunlight...

maybe in small area very short duration, but how does it do on the infared light? How about....hell I've been around engineers too long. Need to go burn some ammo, good thing that between two of us that I know are recieving ammo at Benton we'll have at least 30,000 rounds, now if I can just find a good spotter to hang around that long.

Innocent

[steve b.]

Mary,

"Position of the face on the stock, and other physical things occur with "rail" vs. offhand. However, don't forget that the point that you aim from ('face on the stock') even in a rail gun can change also."

You point out a mistake that most new rail gun shooters make, in that they are solely relying on their eye to aim the rifle, and not the mechanics of the rest. (also with a rail gun - don't touch the gun! get the parallax out and you're set).

To deal with this, I hang my ARA or RBA target with a level, and get the edges square to the level. I also level the rifle and the rail, and since the stock uses steel rails that travel in machined grooves in delrin, the rifle tracks pretty straight - to the point that it moves less than the diameter of the dot on the scope.

Here is a pic of one of the rail guns:



Here is another:



Hope that gives a good idea on the setup

Then, I setup the rail's adjustments to the lines on the target, and once that's done, the mechanics of the rail are accurate enough to span the entire target, left to right about 17", without making any elevation change. Then, using the center dots on the bulls, it can travel up and down and cover all the scoring dots in a straight line with the dot in the scope. This setup is now perfectly square to the target.

As targets are changed, they go in the exact same spot on the target frame, and the same process is repeated.

With all of that said, from what I notice here in the hot and dry SW, my POI steadily climbs during the day. So much so that I have to click it out on my scope or I'm holding off the scoring bull by the 4th card.

It's just my opinion that it's related the increase in temperature and the change in air density. It could be a moon / tide thing for all I know!

[jneihouse]

Have shot very, very little in IR and know even less about the ins and outs of shooting IR.....The off the camera flashes that have came out the past few years are very good and adjustable within an narrow wavelength...The D200 that I'm using now had quite a bit of adjustment built into the camera body...really a neat piece of technology..

Kitty

[Innocent]

Hey if Ducky will not run for president, how about Rambo??? Bet he could hook up with Leggy Sarah and make a winning team?

Kitty,
IR measurements are interesting, especially when dealing with calibrations on the instruments. Done a few photo processing jobs in my early days, light is an amazing thing, both real and artificial and how it is recorded on film and now digitally are all far more detailed than most of the readers on this forum care to know.
Steve,
While I agree that temperature has a lot more to do with bullet trajectory than light ever will, what the chemical factory/computer human body does with the 'garbage in' to the brain is a factor in long distance shooting accuracy.

I've not reached the point of needing to smell powder burning by having a gun clamped in a vice yet, (hope that I die before my body hits that point), but in the overall picture of playing with the precision of rail guns I can acknowledge that tepmerature is a much bigger factor in the POA and POI.

Mary