Talk:Reflector sight/GA1

GA Review

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Reviewer: Jc3s5h (talk) 14:07, 19 July 2011 (UTC) This is a generally well-written, informative, and well-referenced article. I was especially pleased to see the wide range of devices that are covered. I would like to see a more explicit explanation of why parallax is not a problem with these sights.[reply]

ty for the input and noted problem. Effects of parallax was explained per its effects on usage in the "Weapons" section, but yeah, that was scattered and not explained well in the "Overview". Edits have now been made to try to fix that. Fountains of Bryn Mawr (talk) 16:44, 19 July 2011 (UTC)[reply]

Parallax wording

Fountains of Bryn Mawr recently added this to the overview:

Since the optical collimator produces collimated light, light that is nearly parallel, the reticle image produced by the sight is theoretically perfectly parallel with the axis of the device or gun barrel it is aligned with, i.e. with no parallax. Because the light is collimated the reticle can be seen at any position behind the optical window. But this also means, for targets closer than infinity, sighting towards the edge of the optical window can make the reticle move in relation to the target since the observer is sighting down a parallel light bundle at the edge. This gives a error circle equal to the diameter of the collimating optics.

I'm not an expert on optics. Maybe an expert would understand better than I do, but I have trouble with the following points:

"reticle image produced by the sight is theoretically perfectly parallel with the axis of the device or gun barrel it is aligned with". I'm not sure what it means for a virtual image to be parallel with anything. It looks perpendicular with the axis of the gun barrel.
"the reticle can be seen at any position behind the optical window." No, the reticle can be seen only if the observer's eye is nearly on the axis of the collimator.
"This gives a error circle equal to the diameter of the collimating optics." I'm not sure where this error circle is located, so I can't envision how much error this causes at the target. A diagram showing the observer, optics, and target would help understand the error. Jc3s5h (talk) 17:04, 19 July 2011 (UTC)[reply]

I see where it is unclear. Per point 1, the light making up the image of the reticle is collimated (parallel) and that parallel light is parallel with the barrel, or device aiming axis. Per point 2, reference #2 describes "The collimator's pupil is so large that the eye can be positioned at any point within a large cylindrical volume in back of the sight", so yeah, need to describe as a type of cylinder, the eye has to be in the cylindrical volume behind the optical window. Per point 3, the sight uses parallel light so if you have a 2 inch diameter optical collimator and move your eye position from the bottom of the collimator to the top of the collimator the sighting point moves up 2 inches as well, whether the target is a person 3 feet in front of you or a spaceship orbiting the moon the aim point moves 2 inches up that body or 2 inches up that spaceship hull, respectively. "error circle" may be the wrong term since it is close to other technical terms that have a different meaning such as Circular error probable. Maybe it should be described as a "range of movement". Will try to reword and/or will look for other suggestions/edits. Fountains of Bryn Mawr (talk) 02:39, 20 July 2011 (UTC)[reply]

I believe that the reference to parallax is plain wrong. Parallax is the offset fixed of the sight to the gun -- a couple of feet in an airplane. There is no way that a simple reflector gun sight can adjust for this -- ie point a couple of feet lower on the target regardless of distance. I suggest that it be removed. Tuntable (talk) 07:36, 22 August 2011 (UTC)[reply]

"Parallax is the apparent movement of the target relative to the reticle when moving your head up and down," (or left and right for that matter) per this document (page 16). I think you are talking about "Sight Height". Parallax, in this application, is a measure of the accuracy of a sight in relationship to itself (its optical axis). Fountains of Bryn Mawr (talk) 19:05, 22 August 2011 (UTC)[reply]