PARALLAX CORRECTIVE METHODS (Optics Design)
I. REAR (SECOND FOCAL PLANE TYPE) CORRECTIVE ADJUSTMENTS.
This feature is usually a numbered range ring from minimum yardage (usually 50) to maximum yardage (usually infinity) and sets directly in front of the eyepiece, similar to the usual variable power ring but controls the Parallax Adjustment. This is almost always found only on fixed power scopes, due to the internal construction. This adjustment is usually found on scopes of more than 8x and less than 20x. Some Examples are Tasco, Phrobis and Baush&Lomb tactical scopes.
Advantages:
• Is near the shooter and can be reached easily. Cheap to make.
Disadvantages:
• Very coarse adjustment and hard to use, especially on higher power.
• Left eye cannot see the yardage indicator while looking through the scope and movement is extremely coarse.
• Difficult, if not impossible, to make work on conventional variable-power scopes.
II. MIDDLE (TURRET/SADDLE TYPE) CORRECTIVE METHOD
Usually on left side of turret with yardage increments printed around the radius of a third knob. Designed to be easily reachable and adjustable with left hand while looking through scope. An example is Leupold Mark IV Tactical (or NightForce NXS in illustration).
Advantages:
• Easy reachable from shooting position.
Disadvantages:
• Most companies using this style build it in such a way as to not be able to easily read the yardage numbers without shifting ones head from the eyepiece. This lessens the utility.
• With some other brands of scopes we've tested it is difficult to achieve maximum target sharpness with near-zero parallax. There are many reasons for this, including sloppy production tolerances.
• Is very coarse and not as finely tunable, particularly at higher power without putting a very large (3" or larger) knob on, which again, defeats the concept.
• Has more mechanical systems to fail. More expensive to make, if done well
[EDITOR'S NOTE: When using Leupold side-focus scopes, such as the 6.5-20X LRT, lash in the focus knob can lead to focusing problems. When this happens your target is slightly out-of-focus when you've got the parallax "dialed-down" as much as possible. To get better, more repeatable focus, you should rotate the side-focus knob ALL the way forward to the infinity stop before setting the parallax adjustment. Go slowly. If you go past the point where parallax is minimized and focus is sharp, then go all the way back to the infinity stop and start again.]
III. FRONT (OBJECTIVE LENS TYPE)
This is one of the oldest, most proven and still the probably the best and most versatile system optically and mechanically. Either very fine or rapid gain fast threads can be used, depending on the application. If made properly, it can be as rugged and abuse resistant, as the three other types of adjustment, while offering many advantages the first two methods don’t have. This method is usually seen as a fixed objective, (set at the factory and non-adjustable w/o special tools), or fully adjustable by hand.
Advantages:
• Optically the most proven and efficient.
• Mechanically, the most versatile and effective way.
• Historically, fixed objective scopes up to 10x have been most accepted by the military because of ruggedness.
Disadvantages:
• On extremely long scopes can be hard to reach from the shooter’s position.
• Cannot easily see the range or yardage increments from shooter’s position.
• Can Leak easier,( on hand adjustable models), if not made well
IV. U.S. OPTICS "ERGO" ADJUSTMENT SYSTEM
After many years of designing and building scopes for myself and other companies, we think this system, which is a refinement of #3 above, has all the advantages of the above systems and none of the disadvantages. Those advantages are:
• One can see the yardage increments very clearly with the left eye while looking through the scope with the right eye.
• Is easily reachable while in shooting position.
• Has a finer adjustment than knob-turret type designs.
• Can be made to accommodate slow or rapid gain operation, depending on the need and application.
• Can be made as rugged and sealable as necessary.
• Is modularly modifiable for different applications.
US Optics can build all four of the above systems, depending on the need, but prefer and recommend the #4 ERGO system by far.
en fait , le reglage de netteté (focus) avant ou sur le côté corrige aussi la parallaxe
dans le cas d'une lunette non equipée du reglage , c'est la distance entre l'oeil et la lunette ,et l'alignement de l'oeil par rapport a l'axe de la lunette .
donc reglage de l'appui joue en hauteur , + chercher la bonne distance entre l'oeil et lunette , si les 2 sont correctes, faire un mouvement circulaire avec l'oeil en gardant le point visé , la croix de visée devrait rester sur l'objectif ,si on a l'impression que la croix tourne autour du point visé , c'est qu'on ne se trouve pas soit a la bonne distance ou pas perpendiculaire a l'axe de la lunette (erreur machinale et courante ! modification de la position de tir , hauteur d'epaulement,position laterale de la crosse ,position differente de la joue sur la crosse )
en general les lunettes sans reglage sont ajustées pour +- 150 m
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Club : AOC & CTF
Belges réveillons nous , l ennemi est a nos portes , et nous dormons ! mieux vaut mourir debout que vivre a genoux localisation : Belgique ,la Louvière, démocratie moribonde
Que les puces d'un millier de chiens galeux infestent le cul de ceux qui vous gâcheront une seule seconde de votre vie !
et que les bras de ces abrutis deviennent trop courts pour qu'ils puissent jamais se le gratter.
Edité 1 foi(s). La dernière correction date de il y a douze années et a été effectuée par lagaffe.
