Arduino based telescope GoTo controller

[mechanoid]

I wanted a new controller for my Vixen GPDX mount, to replace the ageing SS2K unit that could fail at any time. Although third party controllers were available, I decided to make my own so that I'd get exactly what I needed for astrophotography. Plus I'd get 24/7 on-site technical support !

 

Its based around a Teensy 4.0 microcontroller board (ARM Cortex 32 bit processor running at 600 MHz), which is one of the Arduino family.  The older Arduinos based on the 8 bit, 16 Mhz processors aren't nearly powerful enough for this application, as I discovered the hard way.  The motors on the Vixen mount are DC ones, and this runs the two servo loops at 1 kHz. The optical encoders interface to a separate board, sending the positions via the SPI bus. GoTo moves follow a trapezoidal velocity profile, and are a lot smoother than with the SS2K controller.  I used the onboard real time clock to calculate Sidereal time, but actually it isn't really needed. Just a timer that ticks at Sidereal rate.

 

I made a small handset with fixed x5 Sidereal rate NSEW buttons for star centering.  The front panel has two leds, a green when to indicate that its tracking OK, and a red one if its broken.  A slide switch tells it which side of the pillar the telescope is on. I specifically did not want automatic pier flipping, which can't be avoided with the SS2K. It used to drive me nuts...

 

I wrote an ASCOM driver to let it work with any planetarium program (I use APT), so there was no need for any built in star catalogues. So far its working fine, and I've retired my old SS2K controller.  One unexpected bonus is that the mount tracking is now much more accurate, particularly in declination.  This is probably due to  much stiffer servo loops that those implemented in the SS2K, which wouldn't have had access to such powerful processors as are now available. It seems reasonable to expect that any third party add-on controllers should bring about an improvement as well, since they're probably better at it than I am.

 

So now the mount has a new lease of life, and is even better than when it was new !  Result.

 

 

[TerryMcK]

Great results

[Demon]

Well done from another arduino ascom goto diyer