Hi all,
I have been doing some maths and trying to work out what input speed my stepper motor needs to be doing for my Star Tracker mount. In it's current form, which works out well, it takes the input stepper motor between 46 and 47sec to do one revolution. I wanted to be able to make this more accurate.
From the Stepper motor it enters a 63:1 worm drive, so for every 63 turns of the stepper motor the output of this does 1 revolution. On the worm drive I have a 15 tooth gear, this meshes to a 53 tooth gear, which has an 18 tooth gear above it. From this 18 tooth gear it meshes with another 53 tooth gear, this gear also has a 18 tooth gear above it, this meshes with another 53 tooth gear and is the final reduction. The output to my Tripod head is attached to this gear.
Now the way I see it and this is where I need confirmation, there is a 63:1 reduction of the worm, 15 to 53 gears have a reduction of 3.533333, then the 18 to 53 gears have a reduction of 2.944444. There are two of those..
So 63 x 3.533333 x 2.944444 x 2.944444 = 1929.886272364913748144 reduction. Correct so far?
Now Sidreal time is 23hrs, 56min, 4sec which is 86164 seconds.
So to do 360 degree or 1 rev, the motor needs to do
Sidereal seconds / total reduction
86164 / 1929.886272364913748144
=44.647190476365866588831940649819 sec per revolution.
Does this sound correct? It does to me since the motor input speed is very similar to what I have now, and I knew that wasn't exactly correct.