I have an Aimpoint with cowitnessed ARMS #40L BUIS on my carbine.  I have poor vision, so without my glasses the dot is a horrible mess, probably 15-20 MOA and not even a dot.  I was just playing around with my carbine, and looked at  the dot through the small aperture and noticed that it was considerably clearer than when looking either over the rear sight, or with the rear sight folded (no aperture to look through).  It also works with the large aperture, but not nearly as well.  Does anyone know why the dot looks so much better when viewed through the aperture??

The aperture acts as a lens (light waves passing through it are bent), thus focusing the dot. Same reason people who are shortsighted tend to squint when looking at distant objects without corrective lenses.

As I wear corrective lenses, I get the same effect (natuarally).  I also find that my dot's bloom status is also a function of what and how much I have had to eat and drink, and whether or not I am looking at it early late or very late in the evening.  I kid you not.

Craig

Quoted: I also find that my dot's bloom status is also a function of what and how much I have had to eat and drink Craig

I too have found this to be the case, as the dot quickly degenerates into two separate dots. Past that things get fuzzy, and I wake up on the bathroom floor.

Hey, I was not trying to degrade this thread into a drunken brawl

Very serious about my dot and my physical status at the time.   Lots to eat and enough sleep, and my dots are sharp.  Empty belly and groggy, the dots look like hell.  I am also affected by magnified optics as I am left eye dominant and shoot rifles right handed.  A long day in the field behind magnified optics, and the drive home is interesting.  Both eyes definately out of focus.  No chance of seeing anything that would resemble one clear small dot on my Aimpoint.  One of the reasons I went to the 2moa dot.  A two minute star burst is still smaller than a 4 moa star burst.

Craig

Quoted: The aperture acts as a lens (light waves passing through it are bent), thus focusing the dot. Same reason people who are shortsighted tend to squint when looking at distant objects without corrective lenses.

Actually, the apeture does not act as a lens, and light waves are not being bent.  The apeture has no medium with which to bend light!

What is happening is that you are narrowing the palpebral aperture, meaning you are decreasing the amount of light to be less then the max that pupil is capable of taking in at that focal length.  Same prinicple as f-stops in cameras.  Decreasing the apeture increases depth of focus.  This is also how squinting helps you see better.

Quoted: Quoted: Quoted: The aperture acts as a lens (light waves passing through it are bent), thus focusing the dot. Same reason people who are shortsighted tend to squint when looking at distant objects without corrective lenses. Actually, the apeture does not act as a lens, and light waves are not being bent.  The apeture has no medium with which to bend light! What is happening is that you are narrowing the palpebral aperture, meaning you are decreasing the amount of light to be less then the max that pupil is capable of taking in at that focal length.  Same prinicple as f-stops in cameras.  Decreasing the apeture increases depth of focus.  This is also how squinting helps you see better. I have no idea what you just said, but it sure sounds good!

Hehe...I tend to drop into physicist-speak sometimes.  Basically, by changing the size of the apeture, you change where the incoming light rays converge (focal length).  This changes the distace at which you are able to focus.

Edited for spelling (conferge?  Man, I looked stupid

Quoted: Basically, by changing the size of the apeture, you change where the incoming light rays conferge (focal length).  This changes the distace at which you are able to focus.

Aye, I wasn't using correct terminology.

You should talk to you doctor, if you eye sight is being affected that much by your blood sugar level, that is no a good sign.