Focus IPD Merging

Focus IPD Merging

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Interpupillary Adjustment

To adjust for distance between observers eyes I chose the rotating tops method (see concepts & designs). Since I wanted to limit the moving parts only one top ring rotates. Turning this top manually would introduce movement and perhaps a shift in the image, so I added a motor.

Electronics for Motofocus, IPD and Merging

When reading about the experiences of others who have build binoscopes, one thing is a commonality. To get to a good image you need to follow a lot of steps. After collimating each individual telescope, now you have to align both telescopes to form one image. How to do this depends primarily on the way you build your telescope. Arie Otten has written extensively on this subject and has come up with a workable way of getting to two collimated telescopes with a nicely merged image (see his website for more info).

Getting to this situation is a lot of work (binoscopes are usually not point and shoot), but this doesn’t change once you start observing. Observing with a binoscope requires more procedures. You need to focus two focusers and adjust the interpupillary distance between the eyepieces every time you switch between observers. Also merging adjustments are common during the night, especially when using higher magnifications. This was the main reason why I, like most binoscope builders, motorized all these functions.

To that end I build a handcontroller using two surplus JMI handcontrollers. The handcontrollers connects to a switch box, which in turn connects to the motors for focus, IPD and merging. The motors for focus and IPD are readily available on amazon or aliexpress. You can use the handcontroller to control either the motofocus, or the IPD, or the merging motors in the mirror box.


The trusses are made out of 18 mm carbon rod. The plugs on the end were machined on a lathe, this was a lot of work for such a tiny part of the telescope. On the top the trusses are fastened using an L profile (see 4th image below). For the connection to the mirror box I made truss blocks. Initially I intended to use 7 trusses but luckily I designed the telescope for 11 trusses (more on that in The Build 4) .