The B1 binocular adapter from MagView is an excellent product that does exactly what it is supposed to do...positively connects your cell phone/camera to your binoculars. For years I would just hold my binoculars and my phone up at the same time and get some pretty phenomenal photos but was about the only time i would ever wish i had a 3rd hand to help position and stabilize things! The MagView adapter really streamlines the procedure. Not only is it much faster to get things lined up, you can easily do it with just one hand. It's quick and easy.
A couple of things to note relative to my equipment. The eye cups on my binoculars (Swaro 10x42s) require a clockwise rotation to recess them and the phone I am using has multiple camera lenses and a light sensor (iPhone 14).
From my experience: placing the adapter on the left side of my binoculars is advantageous for two reasons. This obviously forces my camera lens on my phone to line up with the right side of the binoculars and at the same time allows more light to reach the light sensor for the camera since it is positioned skyward rather than toward the ground. With the light sensor collecting more light it seems to focus much faster. TIP Choosing to video will make it focus even faster. The second advantage to placing the adapter on the left side of the binocular is due to gravity acting upon the portion of your phone that is leveraged out away from the eye cup point of rotation... while the magnet is powerful enough to keep your phone from rotating about the eye piece, the resistance it takes to rotate the eye cups on your binoculars is very likely minimal and the weight of the phone will actually cause the cup to rotate... ultimately causing you to loose alignment between your camera and the right side binocular tube. TIP~ just prior to connecting your phone to to your binoculars, rotate the eye cups inward to the stopping location, attach and align camera, then rotate the right eye cup outward just slightly so that it is closest to the camera lense(s) to reduce light between the lens and eye cup.