SkyWatcher14- Debug help please



I'm fitting a OnStep drive to a SkyWatcher 14" Dobsonian and I'm having trouble trying to debug the setup.

The circuit is based on the Solderless Breadboard/Teensy3.2. The circuit and the motors work fine - very smooth (and quiet compared to my old MelBartels GEM). The gearing is identical for both axis, so both axis have the same settings.  I'm sending commands from the Smartphone app. over Bluetooth.

I live west of Sydney Australia.

My initial testing gives a very strange slew.  Here is what I did.
- point scope at South Celestial pole.
- turn on power and connect via bluetooth.
- click Set date and time (correct info sent to Teensy)
- choose to align on RigelKent which should have been a 6 degree slew in Altitude, and a 30 degree slew in Azimuth.

However, the scope moved about right in Altitude, but it did a 400 degree slew on Azimuth!

I've a feeling there is a bug in my site coordinate and/or time settings.

I've attached screenshots from the smartphone app. showing my settings as well as my spreadsheet.

Any help would be appreciated. TIA.


DaveGee ( )


Does manually setting the time zone help? Do you have the WiFi add-on? You could try checking the webpage, if that shows the correct date, time and location. 

Howard Dutton

I would use a PC and ASCOM + planetarium software to get a better sense of what OnStep thinks is happening with the movements...

My guess is the stepper drivers aren't in 16x micro-step mode and that's why it's moving too far.  Just a guess.



I did a couple of things
- corrected an error in my StepsPerDegree (oops!)
- changed MaxAzm to 360
- reversed the direction of the Az motor
uploaded the code to the Teensy

And rebooted my phone and... Sensible slews achieved.  Yay!

Now all I need for all this smoke to disappear and try it out under some stars.

I have a video of the rig slewing on by FB profile...