It may be a bit premature to write it off just yet. By attempting to clean it using water alone you've probably just smeared out the oily residues that were on the surface. To remove oily contamination you need an organic solvent, I would try again using a mix of isopropanol and water (a.k.a. rubbing alcohol). Be careful not to scratch it though. Celestron have cleaning instructions on their website:
http://www.celestron.com/c3/support3...eid=1738&nav=0