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Optics, Mounts, Rails and Sights If it aims your firearm, post about it here.

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  #1  
Old 02-14-2020, 8:30 PM
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Default I've got astigmatism. Why does looking through my RDS thru BUIS help with the starbu

I noticed that if I have the rear MBUIS for lower 1/3 cowitness flipped up, the red dot through the aperture looks crystal clear while outside of the aperture it looks starry.

What is the scientific explanation for that? Just curious. Thanks in advance for your answer!

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Last edited by PogoJack; 02-15-2020 at 2:14 AM..
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Old 02-14-2020, 8:34 PM
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Prolly has to do with where your focal point is (like the 3D image books). IANAO
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Old 02-14-2020, 8:46 PM
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Beats me, but it works for me too.


SMALLEST dot possible ALSO helps. I run 2moa EVERYTHING!
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Old 02-15-2020, 12:43 AM
Oldboyjun Oldboyjun is offline
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Quick and simple explanation here:



I also have astigmatism and have noticed the same thing when looking at the dot of my Trijicon MRO through the rear BUIS. The dot is much crisper and cleaner.
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Old 02-15-2020, 4:13 AM
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My High School English teacher used pinhole glasses.
She said it was to exercise her eye muscles.
Tried them on but had eagle vision back then so no help.
Maybe will revisit the idea and start a new look.

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Old 02-15-2020, 4:27 AM
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See your eye doctor fix you right up. Spend money on anti glare for your glasses. You can put the splatter dot on target and blast away.
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Old 02-15-2020, 5:56 AM
Jesse 2 Jesse 2 is offline
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Same principle applies in sunny outdoors, when your pupil shrinks to smallest size. Dot will become quite sharper. In pitch black darkness, pupil opens up, the dot looks like crap.
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Old 02-15-2020, 6:23 AM
mej16489 mej16489 is offline
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The peephole makes your brain control the muscles in your eye with more precision resulting in overcoming some of the eye's uncorrected vision issues.
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Old 02-15-2020, 6:59 AM
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E=Mc2
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Old 02-15-2020, 8:41 AM
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My vision is no longer fully correctable. I noticed this when I put a red dot sight on my daugther's .22

Astigmatism too severe to wear astigmatism contact lenses.
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Old 02-19-2020, 8:20 PM
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Same happens to me. Thought I was seeing things.
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Old 02-20-2020, 8:31 AM
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The same thing happens when you put a magnifier behind your red dot.
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Old 02-20-2020, 1:24 PM
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Some people have higher order aberrations where glasses won’t fix this.
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Old 02-20-2020, 9:27 PM
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If you're far sighted make a tight circle with your pointer finger and look through the center you'll be able to read without glasses. You look stupid at the store trying to read labels etc. You can also use your cell phone to take a pic of what you need to read.
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Old 02-20-2020, 11:36 PM
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Mostly guesswork: apertures reduce the amount of light coming through, in a tighter 'pencil' of light. Less light against a smaller cross section of cornea, then less light is coming in through the astigmatic part to throw off the laser and give that 'starburst' pattern.
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Old 02-21-2020, 5:54 AM
WalterJones WalterJones is offline
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I still remember well being at a CMP shoot thinking my Aimpoint was broken. Looked up trouble shooting online and stumbled upon the curse of the astigmatism...was i denial till I had my kid look through the optic.

Wonder if we could figure out some kind of filter? Would a polarizing filter work?
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Old 03-13-2020, 10:23 AM
kimw880 kimw880 is offline
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I have the same problem. Can't use EoTech. My aimpoint pro is clear without the starburst effect. Which RDU are you using?
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Old 03-18-2020, 12:48 AM
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When looking through the RDS are you looking at the dot or the target? RDS requires a target focus.
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Old 03-21-2020, 7:40 PM
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Interesting OP I was looking to go award from my red dot due to the starburst effect but now gonna have to try running a rear sight behind it.
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