It would be very difficult, costly and time consuming to modify an old equatorial mount to connect up with a laptop for astro-photography. It may not work after all.
You can try to look for some assistance in the list of local astro equipment suppliers in the websites here :- http://forum.hkas.org.hk/viewthr ... &extra=page%3D1
Alternatively it may be more cost effective and easier to get a new equatorial mount that can be hook up to a laptop right away, such as this one available locally ex stock :- http://www.scopehouse.com/CG5-Mount.htm http://www.celestron.com/c3/product.php?CatID=16&ProdID=92