A rugged adjustable, optical alignment system is well suited for use in low light environments or at night. A rear sight includes a U-shaped array of, preferably, first second and third substantially cylindrical, transparent, tritium vials arranged such that the elongated cylindrical side surfaces of the vials are exposed to define an array of elongated illuminated segments. The array is preferably in the shape of a "U" having a first horizontally aligned vial positioned below a sight notch with a second vertical vial positioned above and to the left of the notch. A third vertical vial is positioned to the right of the sighting notch, above the first vial. In use, a front blade or front post also containing a tritium insert is aligned within the rear sight's U-shaped array of illuminated segments, thereby providing an intuitive sight picture.