here found this

Polish it with steel wool: Use steel wool If the water spots are too tough for terrycloth. Steel wool doesn’t scratch glass, and actually polishes it. Lots of car owners use steel wool to clean their windshields when water spots form on them. You may use steel wool in combination with whatever cleaner you want, whether vinegar or a commercial window cleaner. Make sure the steel wool is super fine grade (grade#0000) or you will scratch the glass


so make sure its the finest grade you can find.

also a 50/50 water/vinigar mix should help.