Aimpoint T-1 and 3x magnifier

[Koshinn]

So I have this setup, and the T-1's dot looks huge and unfocused when using the 3x mag. Logically, I think it's because it's a 4MOA dot and magnifying it 3x makes it look huge, but could this be due to my $100 primary arms "premium" magnifier instead of the T-1?

[Paulo_Santos]

It shouldn't. The only thing the magnifier does is magnifies the dot and the target. I've heard of similar complaints in the past about the T-1 with the magnifiers, but I've never tries it.

[Hmac]

I use my T-1 with an Eotech 3x magnifier occasionally. It turns that 4 MOA dot into an indistinct, comma-shaped blob. Your problem isn't the magnifier, it's that that reticle doesn't magnify well. A 2 MOA dot magnifies better.

http://SSEquine.net/noveskesbr2.jpg

[Mike]

It's not your setup, it's physics.

My more or less educated guess from an engineering point of view is that this "comma shaped blop" is due to the following:

The T1 Micro Aimpoint projects a focussed beam of light (not sure if you can call it a Laser with its properties, probably you could) onto a specially coated glas pane at an oblique angle.
Most of the light is reflected at the surface of the pane and directed towards the shooters eye. A smaller fraction of the total light output of the diode penetrates the surface of the glass and is reflected at the backside of the glass pane.

As the angle of the light is oblique because the (Laser?-)LED sits at the side of the housing projecting towards the center axis of the sight, the dot of the second reflection is a tiny bit out of alignment in relation to the first, brighter dot (as well as change in refraction index, crossing over into another media, yadda yadda...). Thus you will see an oval dot with a brighter and a not so bright part as they superimpose each other a bit at a certain angle (if I remember correctly it's about 45° or so from the vertical).

Google image search found this which shows the refraction part pretty good*:

http://www.3darts.org/livnys/uploaded_images/glass-789255.jpg



You usually don't notice this with the naked eye but when running a magnifier behind the T-1 this effect gets visible.

This effect is different on different models as thickness of glass, type of coating, size of dot and the distance of LED to glass as well as the diameter of glass/tube (affecting the impact angle) varies. I haven't been running the magnifier behind my Comp C, M2 or M4 so far, but I'll check.

So as Hmac said, there may be a difference between the 2MOA and the 4MOA version. But I haven't been able to verify that side by side. But I'll see Mr. Ljungfelt in three weeks. If I have the time, I'll try to ask him about this.

/edit:

*The angle of reflection will be the same as the angle of incidence so the picture is not 100% perfect as it only shows the transmission part. To compensate for these angles the interior sides of the glass panes inside reflex sights usually are concave so that the light will be reflected with the appropriate angle and thus straight into the shooters eye.

[Hmac]

I've used that same magnifier behind my buddy's CompM4 with 2 MOA dot and the dot is much more distinct. Not as crisp as the 1 MOA holographic projection dot on the Eotechs, but entirely useable.

[Koshinn]

I just tried it with my friend's Eotech... worked perfectly. So it's the 4 MOA dot that's the "problem", not the magnifier itself.

Anyone want to trade a Aimpoint T-1 with Larue LT-660 riser for an Eotech EXPS3-0?

[Hmac]

If you're looking at the EXPS 3-0 and don't need/want night vision, consider the OPMOD from Oprtics Planet. It's an EXPS 3 without the night vision and is $100 cheaper.

[Koshinn]

If you're looking at the EXPS 3-0 and don't need/want night vision, consider the OPMOD from Oprtics Planet. It's an EXPS 3 without the night vision and is $100 cheaper.

I figure if I deploy, I'll take the EXPS3-0 with me. :)

[chazthebiker]

It's not your setup, it's physics.

My more or less educated guess from an engineering point of view is that this "comma shaped blop" is due to the following:

The T1 Micro Aimpoint projects a focussed beam of light (not sure if you can call it a Laser with its properties, probably you could) onto a specially coated glas pane at an oblique angle.
Most of the light is reflected at the surface of the pane and directed towards the shooters eye. A smaller fraction of the total light output of the diode penetrates the surface of the glass and is reflected at the backside of the glass pane.

As the angle of the light is oblique because the (Laser?-)LED sits at the side of the housing projecting towards the center axis of the sight, the dot of the second reflection is a tiny bit out of alignment in relation to the first, brighter dot (as well as change in refraction index, crossing over into another media, yadda yadda...). Thus you will see an oval dot with a brighter and a not so bright part as they superimpose each other a bit at a certain angle (if I remember correctly it's about 45° or so from the vertical).

Google image search found this which shows the refraction part pretty good*:

http://www.3darts.org/livnys/uploaded_images/glass-789255.jpg



You usually don't notice this with the naked eye but when running a magnifier behind the T-1 this effect gets visible.

This effect is different on different models as thickness of glass, type of coating, size of dot and the distance of LED to glass as well as the diameter of glass/tube (affecting the impact angle) varies. I haven't been running the magnifier behind my Comp C, M2 or M4 so far, but I'll check.

So as Hmac said, there may be a difference between the 2MOA and the 4MOA version. But I haven't been able to verify that side by side. But I'll see Mr. Ljungfelt in three weeks. If I have the time, I'll try to ask him about this.

/edit:

*The angle of reflection will be the same as the angle of incidence so the picture is not 100% perfect as it only shows the transmission part. To compensate for these angles the interior sides of the glass panes inside reflex sights usually are concave so that the light will be reflected with the appropriate angle and thus straight into the shooters eye.

You know you are at the right forum when it is frequented by really smart folks like this.

[oregonshooter]

Just a thought, but could you put the 3X in front of the T1? Does it have the 4" of eye relief that would be between you and the other side of the T1 if it was mounted all the way back?

You would not be magnifying the dot then if the eye relief allowed the setup.

[Uglyduck]

Thats an interesting idea. I'm curious how the physics would play out on something like that and if a magnifier could be built for that purpose, it would certainly be a change from the norm.

[Paulo_Santos]

Would not work. Can't explain why it wouldn't work, but I know it doesn't because I tried it. LOL.

[FastIndy]

The reason why magnifiers are generally placed behind the optic is that slight misalignment will not change POA. As long as your sighting system is reasonably free of parallax, moving the magnifier will not change point of aim if the magnifier is behind it. Putting the magnifier in front would basically be turning it into a regular magnified optic...or a periscope if your magnifier isn't aligned. Even if they started making a magnifier with the very long eye relief (large objective diameter) and proper optical properties to run in front, you would lose one of the biggest advantages of running one...The ability to switch quickly without the need to rezero.

Run a smaller dot[:D]