Hi Walter;
David Lane had created a nice DSS that used a stand-alone Z80 Micro. It was called the Microguider II, was replaced by the Microguider III which required a laptop or PC, latest is Microguider 5 which also requires a PC.
Check it out at http://www.nova-astro.com/mg5.html

There is a fellow in UK who made a DSS for an LX-10 using a REALLY old Timex sinclair. This should be able to be picked up for $2 at a yard sale.
Check it out at http://www.korner.freeserve.co.uk/lx10/dsc.html