Ok, a couple things to do before the reinstall of the eyecup. Does the turret unde
rneath the eyecup rotate with some resistance, albeit slowly when turned by hand? If so, it's probably good in that the diopter grease hasn't lost all it's flexibility when the grease dries out.
Clean off the area where the cup fits over the eyepiece- both surfaces - the edge of the eyepiece where you will probably see the scratch marks where the grub screws made contact with the interfacing surface of the diopter side turret. Also clean the underside of the eyecup as there's likely residual crap from years of potential contamination that can be deposited in a gritty form that can interfere with a smooth mating of the parts back together. If the diopter turret and and eyecup mate easily together, you can remount the eyecup. Tighten all 3 screws to an equal amount. You can sort of tell if the screws are equally driven if all 3 screws are of the same depth in their respective threaded holes. If one appears further "up" in the hole, loosen the other 2 slightly and tighten the one that need the additional depth. the eyepiece diopter collar should now be able to turn the diopter adjust clockwise and counterclockwise. Do NOT try too hard to turn it. If it take too much effort, you can damage the grub screws/holes in the eyecup. I'm hoping that you will find it turns with some resistance , but turns smoothly without catches.
If that's the case you need to have the binos either in a tripod or some stable mount (a window sill, books stacked on a window sill, a fence post)-some stabile position that can be utilized to site on the utility pole that has some fine detail that can be focused on. Use the center focus and focus using the left eyepiece and bring into sharp focus in the center of the filed view. Then holding the bino steady, turn the diopter adjust until the right eye has a sharp view of the same image. The right eye adjust is made WITHOUT touching the center focus, all done with the diopter side adjust only. At that point if the binoculars have proper alignment, the (and the binocular is widened according to your eye distance, you should see the 2 separate images as one circular image.
Do you wear glasses and know the correction of you glasses? The difference in correction right side / left side can be applied to the diopter scale . But hat can be taken care of later. If you don't know what your correction is, then do the same series of adjustments but use only ONE eye, use the center focus to adjust the left side to sharp, then again with the same same eye to the right side and use the diopter side adjust the image through the right side to sharp. At that point you can loosen the grub screws (NOT OUT!!, simply loose) to the point the eyecup moves separately from the eyepiece turret. You can then align the "0" with the usual line or dot reference such that there is no adjustment made to the 2 sides. At that point retighten the 3 screws. That means if a person using the bino had no correction to both eyes that should be the position for a user with 20-20 vision.
If you have 2 images that aren't merged into one image with the brain/eyes, you have a binocular which is in need of alignment. THAT is another way too long and complicated process.
