Hello Andrew,
It should likely be possible through ASCOM but, personnally, I am not using ASCOM.
More simply, since your telescope comes from SW, the mount must obey to the SYNSCAN protocol (that ASCOM is using).
This is a very simple ascii character serial protocol which, I think, can be direcly managed from IDL (through an USB/RS232 port, depending on your machine).
You may easily find the protocol description on the Web, under ''NexStar Communication Protocol".
Cheers,
Alain.