We hear this question a lot, and really lenses, eyepieces and the and telescope objectives are much tougher than you think.
Just go and buy yourself a good quality 12mm Lens pen, I have used one of these to clean Eyepieces, Canon Lenses and My cannon 5D sensor, for ever, and to this day.
You will not damaged anything, the people that sell this sort of stuff are just covering themselves in case of damage.
The Glass and/or the coating can take a beating stay away from any spray on or apply on liquids, IMHO
Leon
