Barndoor tracker

My new summer project: The barndoor tracker! Huh? What? Yes, a barndoortracker is actualy a very simple device to counteract the rotation of the earth while taking a long exposure image of the sky. First of all we need a motor. A steppermotor with a rpm of 1 would be nice. stappenmotorWell, that has proven to be harder than it sounds. After sifting through some drawers I found one. The problem is: it has a rpm of 1.25. So we have to do some math:

The earth rotates once every 23 hours 56 minutes and 4.0916 seconds (23.9344696 hours). So every hour the rotation is:

360 / 23.9344696 = 15.0410686351 degrees / hour, or:

15.041068635 / 60 = 0,2506844772 degrees / minute.

A M6 rod has a pitch rate of 1 mm per minute so we need to calculate the distance between the hinch and the rod by:

1.25 / 0,2506844772 = 285.69486 mm

So the pricipal drawing would look like this:

barndoortracker princiepe tekening

Next step is the practical implication lol.