The dot in my Aimpoint sight doesn't look round. Is it defective?
If your dot does not appear to be perfectly round, the distortion is probably caused by the way that your eye perceives the dot, rather than by some mechanical defect. Due to differences in the lenses in different individuals' eyes, round objects that subtend areas near 3 minutes of angle may appear distorted in a variety of ways depending on the individual and other environmental influences. Inexpensive red dot sights sometimes have manufacturing defects that can cause the dot to be an odd shape.
A simple test that can be easily performed will allow you to determine the cause of the apparent distortion:
Turn the sight on and look through as you normally would. (This test is easiest when the sight is not mounted on a firearm, but can be performed with the sight mounted as well. Just make sure that the firearm is unloaded and pointed in a safe direction.)
While continuing to look through the sight, roll the sight on its optical axis.
If the dot's irregularities seem to revolve around the center of the dot like the spokes of a wheel, there is a mechanical defect causing the distortion.
If the dot does not roll with the sight, the distortion is caused in the way your eye perceives the dot. This is not to say that you don't have good vision. You can see clearly and still see a distortion in objects this small.
This effect is less pronounced in sights with larger dots. More people will see the dot in a sight with a 10 minute-of-angle dot as being perfectly round than will be able to see a 3 MOA dot as round.
