Hi Jack,
You have a high quality mount, so as long as it is reasonably well polar aligned you should be able to use exposures of 5 to 30 seconds for guiding, or possibly longer.
I never guide with exposures less than a 5 seconds as otherwise the mount is “chasing the seeing” due to atmospheric turbulence. This is the small scale scintillations that cause a star image to move and change rapidly. Any command sent to move the mount to chase this ‘seeing’ will be too late as by then the atmosphere will have changed and the star moved to a slightly different position. To get around this for spectroscopy would take professional grade adaptive optics, but it is not necessary for the spectroscopy we do.
Best wishes,
Andy