Mirror cleaning problem

[Baza]

I opened the dobsonian tube today and there are marks on the mirror.
It's spider sh1t on of the ugliest things to get an anything, it's sticky and aggressive.
Has anyone successfully cleaned this deposit from a mirror, I have already bathed it in the normal fashion and that was unsuccessful.

[sn1987a]

Squirt bottle with distilled water and dishwashing liquid in it. Concentrate a bit of squirting action on the poo and it dissolves away. Rinse with distilled water.

[glend]

You can, if necessary, drag a cotton ball over the surface if needed to dislodge the dirt but after you have tried the advice below. Cotton ball should be soaked in the water/soap solution and discarded after a single pass for a new one. Don't put pressure on the surface just drag it over. Rinse with distilled water and use a puffer to blow off remaining drops. Allow to dry in a dust free place - do not use a hair dryer.