had a question for the vet comp shooters here. at every bench at every distance i set up removing as much as i can see. usually i look for a clean sight picture first and then look at the center crosshairs for movement as i sligtly shift my head side to side and up and down. my question, if shooting the same range from similar benches{our home club} does parallax change from day to day. reason im asking is on days of tough mirage would parallax setting be the same? in otherwords can one use a default setting when the mirage make the bull/ target dance a ton. i realize i may turn the power down but that really not my question though.
parallax, does it change?
- Thread starter fordwrench
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Generally, at a short range benchrest match, a yardage change may come at a time of day when, because of mirage, it is difficult to see small amounts of parallax. To answer you question, If my eyepiece is correctly focused so that peak target sharpness, and absolute zero parallax occur at the same point of objective focus, then I will have no parallax at any distance as long as the objective is set for maximum sharpness.
What Boyd said. Another way to put it is that parallax is a function of distance and 200 yds is always 200 yards, but is always different than 100 yards. So your 100 yd setting will always be the samd, and your 2oo yard setting will always be the samd, but they are always different. Are you confused yet?!
i am not sure if im understood here? More directlyly, if i were to say mark my focus at known yardage same range say 200 to 500yds in good conditions. Would those setting remain a constant or something to fall back on those days with severe mirage?
This is just one guy's opinion. If your eyepiece is properly adjusted, it is focused exactly in the plane of the reticle, and if you then adjust the image of the target so that it falls into the same plane, you will, as it were, have your cake and eat it too. (have no parallax, and the sharpest possible image). Again, just my opinion, it is extremely easy, more common than not, to have the eyepiece very slightly out of adjustment, and when that is the case, you the reticle and the sharpest target image in two different focal planes, which causes one to have to choose as to which is more important, and go with that. For my own scopes, I have worked back and forth between front and back adjustments, making small changes to the point where peak target sharpness and absolute zero parallax occur at the same point of objective focus. I will admit that the objective adjustment may vary slightly from day to day, but when I have made that slight change, to sharpen the image, I still had no parallax. Often I have come across posters who adamantly insist that one should do a single "proper" adjustment of the eyepiece. lock it down and never again touch it. If one is talking about lower power scopes of the hunting variety this may be OK, but for my 36X BR scopes it just does not cut it. I have to do a little fine tuning to get to my goal. Again, I make no claim of expertise, and am just reporting my experience.
I'm not sure what technical point the OP is referring to but I will speak to the subject matter I have experience with. I shoot Field Target where high quality and high magnification scopes are commonly used. Parallax adjustment is used as a means of range estimation and can be quite accurate when markings are set up using "camera lens test pattern" type targets at measured distances. These markings can be "off" a significant amount depending on the temperature of the scope the day the markings were made and the temperature on the day of competition. This variance can be so much so that some top shooters have distance markings made up for different ambient temperatures...so yes, parallax adjustment can easily vary from day to day. Hope this helps...
BoydAllen said:
Never tried or thought of that Boyd. I always adjust the rear to focus the reticle and leave it. But I have had problems with that. (target out of focus when theres no parallax) I'm going to give your method a try. Thanks for the advice.
As far as parallax changing from one day to another, I can't see how this happens. Especially when you have a known value at, say 600 yards, in good conditions. In mirage conditions, how do you know if your known value is still NOT correct. The target is bouncing all over the place anyway. If you try to correct off a mirage it seems to me your just fooling yourself. Just my guess.
thanks guys ! i figured i would have to adjust given the day. boyd, i understand your idea and will make use of it. i guess in the end it is what system you use better show you the results your looking for. for now i will fiddle with the eyepiece and focus and also mark the yardages for severe mirage days and report back if i have anything concrete. thanks!
One more little thing...I never pay any attention to the marks at all. ( on my bench rifles) Once I believe that I have precise eyepiece adjustment that I am looking for, I just crank on the objective till the image is its sharpness, and give it a quick check for parallax, if the mirage isn't too bad. The only time that I use the numbers is if I am using them to range find when shooting varmints. While at the range, I use a piece of masking tape and ball point to make an index mark by the objective scale number that corresponds to the distance that I am shooting at. That way, I can adjust the image till it is sharp, and read the approximate distance off of the objective scale, very much like, but not nearly as precise as the air rifle fellow described.
JohnMill
Gold $$ Contributor
All the stuff everybody said plus Your eyes change from day to day.
Boyd I always wished I could use the numbers but it became apparent early on that it was not going to work for me. I became happier when I just gave it up and treated each day as the first one and never hurry.
John
Boyd I always wished I could use the numbers but it became apparent early on that it was not going to work for me. I became happier when I just gave it up and treated each day as the first one and never hurry.
John
How in heavens name are you guys using the parallax dial for range finding? My Leupold VX3 goes from 400 yards to infinity with less than a 1/4 inch between and no marks. I can pretty well judge 300 - 400 yards but after than I need a range finder. At 800 yards, my drop is 16 3/4 minutes and at 850 it's 18 3/4 That's 16 inches and a clean miss on a prairie dog. I can't see any way to range that close with a parallax adjustment
400 yards covers virtually all of my ground squirrel shooting. I didn't say that is was as good as a rangefinder, but it is better than a pure guess, especially when the terrain can be deceptive as to distance. If I were going to do some serious long range work, I would build a purpose built rifle and buy a good rangefinder, but as it is, I am content with what I have, and am doing. 
Sorry...to clarify: Field Target is a shooting sport using precision air rifles. Targets are engaged at distances between 10 and 55 yards (a 1" target at 50 yards sitting is a pretty tough shot by the way!) Top end scopes (S&B, March etc) are used because they can more accurately determine precise mid range distances down to the foot! That's important given the looping trajectory of pellets. These custom sidewheels allow one to make markings more spread out:jerrschmitt said:
Admittedly, by the time you get past 55 yards, the spacing between yardage is so close as to render this method of range estimation no longer viable.
OK, now I understand.
On an adjustable objective distance scale, the distance between the marks is a function of the "speed" of the threads. As you may have observed, side focus scopes are pretty "quick", which is why there is a need for a much larger diameter knob to spread out the divisions. Let me see...with high rings, I could put a larger diameter attachment around the objective....never mind 
I use one to help fine adjust the parallax, of course they laugh at the home made big wheel on my 20-5-X5- LRT Premier/Leupold.
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