A little Collimation help please

[JohnnyAnonymous]

I'm hoping someone can point me in the right direction here with re-collimating my Barska 15x70mm porro bak-4 binoculars... They've never seem quite right with a bit of a double image that gives me a headache after awhile..

I know there must be some form of adjustment near a mirror..

I've searched the net for information and have come up empty handed..

Thanks in advance.

Johnny

[Bojan]

Johnny, it is very often the case that binos have this problem..
And if yours is of cheap design, you will not be able to do it this way.
Anyway, try this:
The collimation of binoculars is usually done by rotating two eccentric rings around each objective lens.
To reach them, you have to unscrew the thin rim around front lenses, this will expose the screw ring (it has two notches opposite each other). Unfasten this ring, and then you will see that there are two more rings underneath, those two are eccentric. You have to rotate them together and one relative to another to actually move the front lens up-down and/or left right to bring both images together.
Another, but more complicated way is to open the compartrment where the prisms are and to adjust their position by inserting a thin aluminium foil between the glass and the frame, as needed...

You will have to fasten the bino to a tripod or some other suitable stand and point it to the very distant object to be able to control the process.
Or, you may use the laser pointer, mounted such that you can move the beam between the two lenses such that it remains parallel to itself
You can observe the projection of the laser beams on the wall couple of metres apart.
Please note, when the binocular is focused to infinity, if you move the laser beam in paralell fashion across the objective lens, this action should not affect the postion of the projection on the wall. But the change in beam direction (or direction of the binos) will, by the magnification factor (15x in your case).
By adjusting the lenses (or prisms, but I do not recommend this to beginners), you have to adjust the spacing of laser beam projections from both binocular optical systems to be exactly the same as the distance between the centres of the eyepieces. Or you have to bring two images together if you use only your eyes..
Good luck,
Bojan