Why do you need so much precision for such a small telescope? Wouldn't it be just as easy to use traditional visual methods to collimate the secondary mirror to the primary mirror. I am assuming that that is what you want to do.
When I tried to position my secondary mirror in relation to the primary mirror, the process was quite simple. I visually positioned both mirrors so that the secondary mirror sat as close to the centre of the primary mirror as was possible.
When I did it, I did not use a lens. I simply looked through the focuser hole without a lens. When I did this I saw the secondary mirror reflected in the image produced on the primary mirror.
I then adjusted balancing screws and mirror postions until the secondary mirror looked as if it was dead centre on the primary mirror.
That's how I did it. It's not absolutely precise but there again, it doesn't have to be if you think about it.
