“The eyes are the windows of the mind.” is the famous old saying. So, it is very difficult for you to doubt what you are seeing. The merged image of the Binoscope will give you the upmost satisfaction and thrill. But, are you really sure your eyes are perfectly parallel with each other? Now, I will show you the cructial technic to check the parallelism of your visual axis. It is quite easy. Just go back from the eye-lenses so that the distance to your eyes about 30cm. If your adjusting of your binoscope is perfect, you will see the merged Ramsden circles with the targets at the center. But if you were seeing the binoscope with some congestion, you will lose one of the target from the Ramsden circle.
The D is the most important measure when you order the EMS SET. The change of the D will not be accepted in the course of making. The standard D of EMS-UL with IPD-Helicoid is 160mm. If you change it to 172mm,for example, the extension tubes should be added and the three set screws at the end of the first unit will be dummies.