Removing an existing center spot can be tricky. It's easy to start removing the glue and then start spreading it around over an ever increasing area. Isopropyl and acetone are not normally denatured (I'm not talking about isopropyl "rubbing alcohol"). These act quickly and leave none of their own impurities. Pure isopropyl can be found even at Bunnings in little spray bottles for a few bucks. You'll find it where the metho and turps is (you can get a bottle of metho for medical purposes while you're there too
). Isopropyl is great as it is an excellent lens cleaner for eyepieces, which you can't do with acetone.
