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-   -   Red dot, dot size? (http://www.firearmstalk.com/forums/f20/red-dot-dot-size-71914/)

EW1066 09-06-2012 05:14 AM

Red dot, dot size?
 
When Aimpoint and other mfgrs state that their dot is X moa, at what distance from the eye are they making that measurement? If they were to say that the dot is X mm that could be measured on the reflecting surface of the optic. But to say that the dot is X moa is subjective and depends on the distance from the eye. Is there an industry standard for this measurement or does it vary from mfgr to mfgr ? I am curious because I recently saw that BSA now has a red dot with a variable dot. 1 moa to 10 moa. 1 moa sounds great, but if the dot is the same size as the dot in my pentax (4 moa) but measured at a point further from the eye it would be pointless to consider the purchase.

Thanks for any and all answers and opinions.

EDUB

KingTiger 09-06-2012 12:43 PM

I would assume they rate it at the optic's specified eye relief distance.

A 1 MOA dot should cover a 1" circle at 100 yards.

The Aimpoint is parallax free, so I wouldn't think it matters what position your head is in as long as the dot is on target. I like the 2 MOA dot that Aimpoint offers.

I'm not sure if BSA uses such standards.

EW1066 09-06-2012 03:53 PM

I understand what parallax free is, but that isn't the question. A non magnified optic has unlimited eye relief. Since moa is a measurement of angular space it changes with distance from the point of origin. If the dot size is measured at 4 inches from the eye and determined to be 2 moa. If you move that dot to 2 inches from the eye it is now 4 moa because it takes up more of your field of view. So the apparent dot size depends on the distance of the dot from the eye. I just want to know if there is an industry standard for the measurement of that dot in order to determine the "apparent" moa coverage of the dot.

EDUB

ZeusEcho 09-07-2012 05:31 PM

Quote:

Originally Posted by EW1066 (Post 930487)
I understand what parallax free is, but that isn't the question. A non magnified optic has unlimited eye relief. Since moa is a measurement of angular space it changes with distance from the point of origin. If the dot size is measured at 4 inches from the eye and determined to be 2 moa. If you move that dot to 2 inches from the eye it is now 4 moa because it takes up more of your field of view. So the apparent dot size depends on the distance of the dot from the eye. I just want to know if there is an industry standard for the measurement of that dot in order to determine the "apparent" moa coverage of the dot.

EDUB

I may be wrong but I think the dot size is in reference to the target. If you move your head closer to the optic, both the dot size and target size should increase right?

Quentin 09-07-2012 05:53 PM

Quote:

Originally Posted by ZeusEcho (Post 931897)
I may be wrong but I think the dot size is in reference to the target. If you move your head closer to the optic, both the dot size and target size should increase right?

Not even close to true. Think about it, you're talking just inches from the eye to the dot which makes almost zero difference to the scores or hundreds of yards to the target.

drvsafe 09-07-2012 06:12 PM

Quote:

Originally Posted by ZeusEcho (Post 931897)
I may be wrong but I think the dot size is in reference to the target. If you move your head closer to the optic, both the dot size and target size should increase right?

I believe you're correct.

Quote:

Originally Posted by Quentin (Post 931926)
Not even close to true. Think about it, you're talking just inches from the eye to the dot which makes almost zero difference to the scores or hundreds of yards to the target.

The dot size doesn't change, only in its appearance to the eye since the distance to and from the optic will cause the dot to "appear" larger or smaller as you move to or away from the optic. But the dot is measured against a target at a specified distance; "...a 1 MOA dot should cover a 1" circle at 100 yards", not appear to be X size to your eye depending on how far or close you are to the optic. That 1" circle will appear larger or smaller as well as you move to and away from the optic.

1 inch or 4 inches away from the optic is going to make only a negligible difference in the appearance of size to both the dot and the target.

Quentin 09-07-2012 07:30 PM

Quote:

Originally Posted by drvsafe (Post 931937)
I believe you're correct.



The dot size doesn't change, only in its appearance to the eye since the distance to and from the optic will cause the dot to "appear" larger or smaller as you move to or away from the optic. But the dot is measured against a target at a specified distance; "...a 1 MOA dot should cover a 1" circle at 100 yards", not appear to be X size to your eye depending on how far or close you are to the optic. That 1" circle will appear larger or smaller as well as you move to and away from the optic.

1 inch or 4 inches away from the optic is going to make only a negligible difference in the appearance of size to both the dot and the target.

Do you write DNC speeches? :D

drvsafe 09-07-2012 07:37 PM

Quote:

Originally Posted by Quentin (Post 931999)
Do you write DNC speeches? :D

(...um, ouch)

Quentin 09-07-2012 07:43 PM

Quote:

Originally Posted by EW1066 (Post 930487)
I understand what parallax free is, but that isn't the question. A non magnified optic has unlimited eye relief. Since moa is a measurement of angular space it changes with distance from the point of origin. If the dot size is measured at 4 inches from the eye and determined to be 2 moa. If you move that dot to 2 inches from the eye it is now 4 moa because it takes up more of your field of view. So the apparent dot size depends on the distance of the dot from the eye. I just want to know if there is an industry standard for the measurement of that dot in order to determine the "apparent" moa coverage of the dot.

EDUB

We need to get this back on topic - the posts by EW1066. Dot size does appear to change (to the eye) as the eye to dot distance changes. Is there an industry standard for "eye relief" for the RDS (all brands) or does each manufacturer set the distance as they prefer? (And thus have an opportunity to claim a better MOA)

drvsafe 09-07-2012 07:54 PM

IMO the MOA is not measured from the eyepiece out it is from the last lens of the optic out. Thought it may appear different in size in effect it's not.

Someone correct me if I'm wrong...


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