I have set out to build a star tracking camera mount to use for astrophotography. I am using Arduino Micro, Pololu A4988 Driver and a stepper motor. I have attache my stuff and am able to run the motor with basic commands. The boards, the motor and wiring seem to be okay. But the final programming remains.
I am a structural engineer and do have a bit of programming experience as a hobbyist so I am not shy with technical stuff and programming lingo.
The mount works when it rotates with an angular speed that matches the angular speed of the planet (sidereal speed). And to achieve that, the screw moves in a linear fashion.
The issue is that the linear speed of the shaft which is driven by the stepper is not linearly related to the angular speed of the mount. And since the angular speed is of paramount importance, we need to vary the screw rotation speed in order to keep the angular speed at the right value.
The board will be programmed to run for 180 minutes which is when the mount has rotated about 45 degrees.
When I program this into MS Excel, I notice that with full steps (200 per revolution), I need to adjust the speed at various locations in time. The first adjustment, for example, takes place at t+36 minutes at full step (18 deg per minute). At 1/16th micro-step per minute (through the Driver) that initial adjustment needs to be made at t+14 minutes from 4032 steps per minute to 4031 steps per minute, and the subsequent adjustments are more frequent with the micro-stepping than they are with full-stepping.
What I am planning on doing is to perform a few loops at given time minutes. And before I get into that I was wondering if anyone here has any suggestions or knows about how others may have done something like this.
Thanks much in advance.