As mentioned in several prior blog posts (Tech – The Telescope Mount, Tech – First Hardware/Software Test, Tech – Alignment & Guiding (Take 3) – Fail, Tech – Telescope Control (Part 2) and Tech – Using Renishaw Absolute Encoder) we plan to use absolute encoders on our telescope mount.
As we found out, the Sidereal Technology SiTech Servo II supports absolute encoder we decided to go for it. To be able to connect the 26bit Biss-C compatible Renishaw Resolute read heads to the SiTech Servo II (which speaks RS232 and not Biss-C) we needed to obtain a small interface box provided by Sidereal Technology: the so called LBB (Little black box).
Essentially it is a prtocol converter which converts the Biss-C protocol electrically and logically to the RS232 interface of the SiTech controller.
Therefore you find some level converters and a small microcontroller inside this box.
So what’s next?
We now have to order the correct sized encoder rings and read heads (in our case the 413mm diameter ring for the RA and the 200mm diameter ring for the DEC axis) and once we got them adapt the mount to be able to mount the rings to it. The main problem here will be to find a suitable and easily adjustable read head mount (the tolerances here are quite narrow). But let us discuss this in another post.