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New to forum, entirely different question

My project has almost NO load to drive. Also, the motor will never change speed, be stopped , or reversed.
So most of the problems that you folks are concerned with don’t apply to my situation.

I have a 200 step/rev stepper motor with an integral 18:1 gearbox attached. The output shaft therefore has
3600 steps/rev.
It is directly coupled to an opaque, almost weightless, plastic disc with an optical interrupter slot on the edge.
Centered over the drive shaft is a 90 degree prism (10mm) into which a laser beam is co-linearly directed.
The effect would be a sweeping laser beam moving 0.1 degree per step with a zero position reference
provided by the optical interrupter. (The electronics for zero detection is entirely synchronous.)
The idea is that the anti-phase of the step pulse would clock the data from both the zero interrupter and an
external optical sensor looking for the beam as it sweeps by while clock pulses driving the stepper controller
would also clock a 4 digit decimal counter, the value of which would be latched by the external laser
I need any and all helpful guidance on the electro-mechanical operation of the stepper motor so that I get
STABLE values from the external laser pickup. Although a short sweep time would be desirable, more
important is repeatability and accuracy.

i.e., I realize that at high step frequencies, the actual “steps” from the motor will almost disappear and that
the actual motor position will be offset from the edge of the clock pulse, but that is okay as long as that
“slew rate” error is consistent from one step to the next.

If you’re having trouble visualizing the setup, please ask questions, and thanks for any suggestions.

If you want a constant speed out of a rotating flywheel, adding mass to it will help increase the stability of its rotation rate. Do you know what rotation rate or step rate you want from your system? How stable does the rotation rate need to be?