I don’t know about pointing for Spectroscopy specifically, but in general even with a small field of view on the guide camera you could try plate solving. For locating variable stars I use APT’s Goto++ feature which takes an image, plate solves, syncs the mount to the current location and issues repeat goto commands until it is within a specified tolerance of the required location. I don’t see why it would not work with a spectrograph guide camera instead of the main imaging camera. Just connect APT to the guide camera use the Goto++ function the shutdown APT are start guiding as required.
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