Just picked up an ACOG in a trade. It is used, but new to me and the first Trijicon optic that I have owned. Upon first handling the optic (at night) I noticed that the reticle was dull and slightly blurry, but I was told before that the optic had been in a safe for over a year. I have had the scope for 3 days and the reticle has gotten much, much brighter, but it is still not fully bright indoors. It is fully bright outdoors in the sun. My question is, how long should it take the tritium in the optic to be fully "charged" up where the reticle is very bright indoors as well as outdoors?

I am really confused, so this is a tag.

the part that glows at night is called tritium I believe, it is a chemical
it glows, and I think the older it is the less bright it is

we install what we call nuke exit signs at work not sure what the real name is, they all have expiration dates
I think the longest ones we get can last 13 years and probably have something similar inside them

they are barely visible in light, but glow okay in total darkness


I dont think the tritium gets brighter outside if anything you wont be able to see it in light
you may be seeing the fiber optic if your model has that, even in low light
thats why I always liked those

During the day or indoors under light the fiber optic tube is providng the light to illuminate the reticle. Place your hand on top and you can see how this can be controlled. If you want to see the tritium, get in a closet with the light off and look through the scope. The more your eyes adjust the better you'll pick up the reticle.

The reticle is not going to get any brighter than it already is in the dark.  Just dimmer as the tritium ages.  The brrighter you are seeing during the day is coming from the light the fiber optic tube is picking up.  It will pick up ambient light indoors and out.  But in total darkness it will only be as bright as the tritium can put off at its age.  They usually last 10-12 years.  I have 2 that are 6 years old.  I really can't tell that they are any " dimmer" in total darkness than the day I bought them, but I am sure they are a little.

Hope this helps.

A model number would be helpful, however from what you describe, it sounds like you have a TA01NSN.  This optic's reticule isn't as bright as Trijicon's other models.

Tritium is a radioactive isotope of Hydrogen. There is no "Charging" required.. The glow comes from the Isotope decaying. It has a Half life.  The reticle is not going to be that bright . You have to be in the dark and let your eyes adjust for about 20-30 mins and then you will see it. Trijicon even states this in the ACOG manual.

Thats why you have the Fiber optic tube on the top, to allow light in to illuminate the reticle during the day.

Common mistake.. People grab one, walk into a room, shut off the lights and say " Hey, I can't see the reticle". You need to have your night vision adjusted to see it... and that takes a good 20-30 mins.

I can walk in a room shut off to daylight and flip the light off and 2 seconds later see the reticle just fine. Not as bright as an Aimpoint by any means but I can see it fine.

Well then your the exception...

Had two different ACOGs a TA01 LAW (crosshair) and TA31F.

Had to use it during night at work and it wasn't sufficient enough for areas with a lot of varying light conditions. The TA31F fared slightly better because of the fiber optic. Some guys I heard tape small chemlights to the fiber optic for more illumination.

The cost of replacing the tritium is almost as much as a new ACOG.

I have since switched to the LED ACOG.

Tritium is a very interesting, an isotope of Hydrogen.  The glow comes from the decay of Tritium, with a half life of 12 years.  Meaning after 12 years, the glow will appear to be half as bright.  I have a set of Trijicon night sights on a Sig 229, purchased new in 2006.  The box had 2005 marked by the dealer, so just the pistol alone is approaching 10 years,  the sights were more than likely older.

The sights are dim, can still be seen, but I can see they will need changing next year.

As far as acclimation to darkness, 15 to 20 minutes is the typical norm, to get the full effect and range of brightness of the Tritium sights.

I took some nuclear engineering courses as electives in college and even after 33 years, I still remember the details, it was very interesting

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