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parallax in a riflescope

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parallax in a riflescope

Postby opticsplanet.com on Mon Oct 11, 2004 12:51 pm

[quote]

> Good morning
> I would like to know why some rifle scopes have crosshairs which seem
> to move if the shooter moves the position of their eye. This tends to
> move the point of impact if the face and eye are not exactly in the
> same position every time...Thanks ....Ray
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Postby opticsplanet.com on Mon Oct 11, 2004 12:54 pm

Hi Raymond

What you describe in a riflescope is something called parallax. Every riflescope is factory set to be focused at a specif range, usually 100 yds. If you shoot at ranges other than this range, there will be a small amount of optical error called parallax.

To put it simply, parallax will cause your crosshairs to appear to be on a spot where they are not. For large targets such as deer, this is not a major factor since error due to parallax will amount to little more than a couple of inches in point of impact at five hundred yards and considerably less at closer ranges.

For really small targets, however, this is a significant amount of error. Varmint hunters and target shooters therefore choose riflescopes with an AO (adjustable objective). An adjustable objective allows you to focus the riflescope exactly for any range, therefore eliminating parallax completely. If you will be varmint or target shooting, an AO is well worth the added expense.
----------------------
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http://www.OpticsPlanet.com
Phone: (888) 263-0356
Fax: (847) 574-6820
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Site Admin
 
Posts: 4044
Joined: Tue Sep 23, 2003 11:18 am
Location: Prospect Heighs, IL