Do you have confidence in being able to tell your heliostat to move to a certain position, and know with confidence that the heliostat did infact move to the desired position?
The test I would perform is as follows:
If you position a laser pointer so that it points onto the center of the heliostat mirror, and the reflected beam comes straight back into the laser pointer, we call this position (0,0). Leave the laser pointer in this fixed position.
Now, tell your heliostat to move, say, 10 degrees, in either azimuth or elevation.
You should expect the reflected laser beam to have moved double this angle, namely 20 degrees.
Using trigonometry, you should be able to confirm if your mirror is positioning itself correctly.
Then, move nirror to 45 degrees, and see of laser reflects at 90 degrees.
Do this in both the positive and negative directions, and in both the azimuth and elevation axis.
Thats what I think is important to do first.