Star tracker made of Lego bricks

After discussing with some of my collegues, I gave myself the chanlenge to create a star tracker.

After a few google search, I first tried the typical barn door tracker. It is made out of 2 recycled piece of wood, hinge and one chocolate spread cap (for the knob). The good point of this tracker is that it was very cheap to do.

I found it difficult to orient and hard to prevent from showing vibration blur for any zoom over 50mm.

There is the first prototype:

I then tried to install a motor on the shaft which was a big mistake. The design was simply not done to be driven by a small motor. Furthermore, the speed was an issue. I initially tough I could use a 20 RPM 5V motor with PWM to reduce its speed until ~ 1 RPM but the motor was just stucking.

So I made a brand new prototype from scratch. I used Lego Brick for the gears and I drive directly angular velocity which is by far better than the barn door Arctan variable precision/velocity. For the Controller I use a DSPIC30f2010 which is awesome controller. They are also way less expensive than Arduino for this type of application.

The second version look like this:

The velocity is controlled by an opto-coupler, but a stepper motor could be a cheaper solution. (requiering less gears, no opto-coupler and probably could offer faster rewind time)

The allignment is done by setting the angle of the tripod to the actual latitude angle, then gears are alligned to point to the north. Using my ball head I can then point the camera in the desired direction. It is a bit weak, but it can drive precisly for hours on batteries. A futur improvement would be to add a variable counter weight to account for the angle and the zoom extension.