I don't know about the reticle in question, but in general, they are mesh, not textures. If the one you want to change is like the rest, you will have to alter it in a 3D program and re-export.
No, the cross hair can be adjusted in NIFScope.
I have this scope in my Data folder as well (Data\meshes\FOOK\interface\hud\Illuminated_MilDot_Smal_scope01.nif), so I opened it up. Here is how to adjust it.
Figure out what adjustment you need to make to center the cross hair (move it left, right, up or down).
Make a backup copy of Illuminated_Mildot_Smal_scope01.nif, then open your working copy in NIFScope.
1. In the Block List area, expand the BSFadeNode (Scope01) block, then the NiNode (Inner Lens Shading) block.
2. Right click on the NiTriShape (crosshair_post) line, and select Transform, then Edit.
3. In the dialog box that comes up, edit the values for Translation (X moves left/right, Y moves up/down,
Z moves front/back).
4. Click accept, then right click the NiTriShape (crosshair_post) line again, and select Transform, then Apply.
5. Repeat steps 2, 3, and 4 on the NiTriShape (crosshair_dots) line, entering the same values as you did for (crosshair_post) in the Translation values.
6. Save the file, exit NIFScope, and check the accuracy of the scope in game.
It might take you a couple tries to get the cross hair dead-on, but hey... ever sighted in a rifle scope in real life?
Fire three shots, look at your pattern on the target, adjust the scope.
Fire three shots, look at your pattern on the target, adjust the scope.
Keep doing this until you get your pattern in the bullseye.
Pretty realistic, huh?
Good luck, and if you FUBAR your working copy of the nif file, you can delete it and resort to your backup copy to try again.
Any problems, and I'll try to help you out.