Thanks all for your thoughts and advice. I got what is advertised by Rother Valley Optics as a ‘Skywatcher SynScan USB adapter’ … and it works (at least - it does in my lounge) I go straight from my RPI4 into the SynScan box, bypassing the HC completely, and fire up Indi using EQmount driver. I believe the RVO gadget is based on a Prolific chip. All I need now are some clear skies to test it out properly, but it looks very hopeful.

Thanks again.

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