In order to take pictures with the phone, it is important to remember that it behaves as if it were a human eye. A telescope, binocular or monocular, is designed to adjust the focus and project the image through the eyepiece of the eye lens. Therefore, the first lens on the phone has the same function. It can be concluded that the lens must be at the same distance from the lens on the eyepiece in the position where the human eye is positioned to see what the optical instrument is projecting. And it is at this distance that the field is best seen.
All telescopes and binoculars have a separator that is retractable for those who have glasses and cannot get so close, so they can look the same as those who do not have them and need to install the separator, or just move a little more, about 1
The system to be built should be easily adjusted at this distance and put the lens of the camera in the phone's eye position, in order to take the photograph or film, in addition to securely attaching and maintaining the stability of the device.
I have tried several switching systems and manufactured and refurbished several connections for the phone. In fact, at https: //www.instructables.com/id/Adaptador-LG-G5-… I published one of the first ones I did.
The one I now present is "phenomenal" (to say about the father), easy to use and easy to manufacture, only the components mentioned and the tool that someone bricolajero has accumulated throughout his life are needed: drill, bits, files, saws and hammer. No knowledge of mechanics or drawing and … You know what more. I have made it for about 18 euros, compared to 40 of the cheapest commercial, which is not "Chinese", which even has them for 3 €.