Red dot, dot size?

Discussion in 'AR-15 Discussion' started by EW1066, Sep 6, 2012.

  1. EW1066

    EW1066 Member Supporter

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    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
     
  2. KingTiger

    KingTiger Member

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    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.
     

  3. EW1066

    EW1066 Member Supporter

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    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
     
  4. ZeusEcho

    ZeusEcho Member Lifetime Supporter

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    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?
     
    Last edited: Sep 7, 2012
  5. Quentin

    Quentin New Member

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    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.
     
  6. drvsafe

    drvsafe New Member

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    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.
     
  7. Quentin

    Quentin New Member

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    Do you write DNC speeches? :D
     
  8. drvsafe

    drvsafe New Member

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    (...um, ouch)
     
  9. Quentin

    Quentin New Member

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    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)
     
  10. drvsafe

    drvsafe New Member

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    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...
     
  11. JonM

    JonM Moderator

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    a true 1x rds with a 1 moa dot covers 1 inch at 100yds regardless of how far your eye is from the sight itself.

    what gets confusing is that to get a true 1x through glass is not easy as it would seem. you would think its easy to get 1x but its not. its one of the reasons that aimpoints arent cheap. looking through glass of any thickness it either magnifies or reduces the image. for it to be 1x the glass pane has to be flat, smooth, and uniform in thickness.

    its not too hard to make delicate glass panes 1x, happens all the time with microscope slides cheaply. making high impact durable glass 1x... not easy

    so with cheaper optics like bsa, vortex, leupold etc you will get a shift in size depending on where your eye relief is. with things like eotech and aimpoint you get an optic that doesnt matter what your eye relief is. hence the confusion.

    now all that being said no rds is going to give good results in terms of shooting for super small groups past about 50yards. so if a rds is 2.1 moa to 2.9 moa really doesnt matter much in terms of landing rounds on target. the purpose of a rds is to land hits inside an 18" circle at any given range in the rifle's effective range. i would say features, durability, ease of use, battery life, clarity in different light situations, and speed are more important factors in picking a red dot sight rather than worrying about exactly how big the dot is.

    no rds is a target optic by any stretch.
     
    Last edited: Sep 7, 2012
  12. JTJ

    JTJ Well-Known Member Supporter

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    And that is why I like a 1-4x scope with an illuminated reticle.
     
  13. JonM

    JonM Moderator

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    Thecheapest actuall 1x variable scope ive come across are the nightforce 1-4x. Everything else ive seen is between 1.1-1.9. My nikon african monarch 1-4x is actually closer to 1.2-4x. Kinda disapointing to figure that out when trying to cowitness buis through a supposed 1x scope.

    I too prefer either a variable scope or a fixed power for ar15 or just plain iron sights. My wife likes her aimpoint but she wants a scope for her ar15 to go with it.
     
    Last edited: Sep 8, 2012
  14. AgentTikki

    AgentTikki New Member

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    Get the best for all worlds. Scope it and put a rds on a 45 degree mount.
     
  15. EW1066

    EW1066 Member Supporter

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    I can accept that by definition a 1 moa dot covers 1 inch at 100 yards. But the apparent dot size (MOA COVERAGE) is ENTIRELY dependant on the distance of the dot reflecting surface from the eye. The end of my index finger can be a 1 moa aiming device if I could get it far enough away from my eye. The point of a pencil can be 10 moa if you could focus on it that close to your eye.

    So again my question is; Is there an industry standard that states that a dot of x mm on a reflecting surface x inches from the eye is x moa? The size of the dot is on the reflecting surface is the only fixed quantity. EVERYTHING ELSE IS A VARIABLE. So without an industry standard or a published standard used by each different mfgr, how can we objectively shop for a sight with MOA of the dot as a criteria for selection?


    EDUB
     
  16. EW1066

    EW1066 Member Supporter

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    Just to be clear. The only reason I'm hung up on this, is because I can't find a decent answer anywhere. I'm not trying to be argumentative or stubborn. I just have a difficult time accepting something at face value, something stated as a hard fact (when there are unsettled variables), which forces me to trust the sales material. I have been in retail far too long to trust the sales material.

    EDUB
     
    Last edited: Sep 9, 2012
  17. SSGN_Doc

    SSGN_Doc Well-Known Member

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    If you really want consistent dot size, get an EOTech it is a holographic retire and does remain the same size in appearance to the eye whether it is up close or out in a hand guard. I have seen this first hand at the range trying different mounting locations.

    I have not tried this with a red dot sight though. Maybe I should. I never really worried about if because I never think of red dots as a precision sight so the difference in dot size never seemed to matter to me. I'll pull out and detatch it and see how the dot behaves as I move it away from my eye with the dot on something to see if it covers more or less of the targeted object.

    I would bet that there is not an industry standard though.
     
  18. SSGN_Doc

    SSGN_Doc Well-Known Member

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    Moving my Bushnell TRS 25 red dot from the rear of the receiver out to full arms length away while holding teh dot next to a circle on my fence I can see no perceptable change in the dot size relative to the target. Must be part of the engineering.