General rule to always remember. If the reticle or dot is seen with your unaided eye no matter how dim it appears in pitch dark, it's way too bright for a Gen 3 device. As Mavrick stated, you can actually burn the image of the dot or reticle onto your NV tube if it's too bright. Some low end Gen 2's can get away with a very dim reticle or dot, but in most cases insure you have a MRDS that has NV compatible brightness settings to avoid burns.
Vic