It's been a long time coming, but I've finally got a stepper motor drive on the grating of the Classical spectroscope (
http://www.iceinspace.com.au/index.p...63,339,0,0,1,0 )
The key, at least for me, was obtaining a suitable controller to give reliable single pulses, combined with a 0.5A motor. The USB stepper controller kit from Surplus Shed did the job!!
The motor is geared 7:1 to the grating shaft and gives 1.1 degree rotation per pulse. For the LPI/ DSI/ Webcam this provides one frame position per pulse, and 2 pulses for the MX7c.
To get from the zero position to 380nm the number of initial pulses varies with the grating ie 300lpm-6pulses, 600lpm-13pulses, 1200lpm-25pulses.
This set-up makes things much easier at the scope, and the small handpaddle with a pushbutton and forward/ reverse switch is very convenient.
This combined with the beamsplitter in the Meade OAG housing has given an excellent outcome!!!