Gday Barry
You are correct that there is a special Meade supplied cable that can be used via the Aux port, but as noted, it is not a simple cable, it has active electronics in it. People need to clearly understand that.
The Aux vs Rs232 ports have the following mapping
Pin 1 Gnd vs Rx
Pin 2 Dat vs Tx
Pin 2 Clk vs n/c
Pin 4 12V vs Gnd
so plugging a std wired ( Meade ) serial cable into an Aux port
ties the cables Rx line to the scopes ground
and the cables real Ground gets 12V put back into it.
( Meade had 4 pins for this function, why they never standardised to prevent this sort of thing is beyond me )
Andrew Johansen Melbourne Australia