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So let's be generous and call it a 300 tooth main gear. 0.9 deg / 300 = 0.003 deg, which sounds small but.... multiply by 3600 arc sec / deg and you get 10.8 arc per step, yikes! Completely unusable by a factor of 100! Something must be wrong in the translation.
BTW 0.9deg steppers are hardly hi-resolution or anything to write home about, that's only a standard stepper motor being operated in half step mode, the same garden variety is used in the robofocuser for example. The other issue they will have with steppers is a very poor torque vs velocity curve. This is why for example the digital drive that came with the original G11 could only go about x32-x64 sidereal, and still had vibrations problems from the stepper jolts while tracking...
EB
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