Both Eyes Open

 A remembrance from the common shooter...

Old timers will remember the AN/PVS-2 "Starlight Scope" as one of the first generation night-vision optics.  

One thing I remember is that by 1980, almost no one in the operating forces of the Marine Corps knew how to properly mount the thing to the M16A1 service rifle.

Folks would invariably bolt it to the top of the rifle through the little hole in the rifle's carrying handle.  That blocked the view through your iron sights, and forced you to come off your stock weld to peer through it.

In Beirut Lebanon, though, we figured out a better way.

The scope came with a funky bracket that most folks left in the bag.  That bracket allowed the scope to be mounted to the port side (shooter's left side) of the rifle instead of being in-line with the sights.

As dusk approached each night, we'd mount our scopes on the left side, then aim in on a streetlight 300 yards away with iron sights.  While the shooter held steady on the iron sights with his right eye, he'd also look through the scope with his left eye, keeping perfect stock-weld.  You'd then ask a buddy to turn the knobs on the scope as you directed him to get the reticle pattern on the same streetlight.  

Zero'd the scope every night using this technique, and shot with both eyes open!

Good shooting!