parallax confused

[aldar]

I did some searching and found a definition for parallax but I'm still a little confused. When a scope is marked as "parallax free at 100yds" does that mean the scope is set so the target and crosshairs are both in focus together at 100yds? so if you had an animal at lets say 200yds and zoomed in on it, the crosshairs  would then be a little out of focus?   also saw some scopes marked as "AO". I know this means adjustable objective.Am I right in assumming that means you can then adjust the scope so both the animal and crosshairs are in focus together at any distance?

[victorcharlie]

Focused on the same plane, meaning the crosshairs and the target are focused on the same horizontal plane.

If you bag the rifle solidly and center the crosshair on the bullseye and move your eye around the scope, if the parallex is adjusted correctly the crosshairs won't move and will stay centered on the bullseye.

If the crosshairs move to different locations across the target while looking from different positions then adjust the parallax........

If you mount the rifle differently, and the parallax is out of adjustment, the point of impact will change.....

The problem is greater at longer ranges and higher scope powers.......and is not so much of a problem at close range and low power.

Hope this makes sense............

[PA-Joe]

The eye piece has an adjustment to focus the hairs (make them clear to view). On an AO scope there is also a front lens adjustment that will help focus the target (make it clear). You can use this adjustment as a range finder.

[aldar]

Thanks guys, I think I get it.  the scope is set so that 100yds the crosshairs will stay on the same point of impact even if I were to have chaged my line of sight thru the scope a little by moving from side to side or up and down- right? so anything beyond 100yds would mean that I would have to keep the same exact line of sight thru the scope to consistantly hit the same point of impact-right? sorry if I'm seem a little slow on the uptake, just trying to understand better in terms I can relate too

[Woodbutcher]

 Ok, so how much of a problem would it be to mount a scope ment for a centerfire on a .22, and use it at less than 50 yards? For squirrel, maybe? A one inch tube gives a much better picture than the .22 scopes that I've used, and I have a 4 power that I'd like to put on my .22.
 Would parallax cause problems, practically speaking?
                                                                            Woodbutcher

[victorcharlie]

Aldar.......You are some what correct. 

The potential for Parallex error is greater as the range increases and at higher scope power.  At 200 yards or so, improperly adjusted parallex with a scope above 8 or nine power, the error can easily open a group up by several inches, depending on how consistent you mount the rifle.

Woodbutcher, at the ranges a .22 works at there is no reason not to use a centerfire scope.  I keep reading about air rifle scopes and the need for the adjustable objective to adjust down to 7 yards but the error would be so small at 7 yards that I don't see it as a problem. 

I've used centerfire scopes on .22's for years and currently have a 1 inch tube 1.5 X 4.5 mounted on my .22lr squirrel rifle........

[Woodbutcher]

 victorcharlie, your answer means more to me than any fancy mag article. Experience! Many thanks!
                                                                  Woodbutcher