This is the 20cm telescope mirror from “Starbuck”, Kim’s newtonian on a Dobsonian mount. Having just come back from the RASC General Assembly, she has refilled the motivation reservoir and wants to do some observing… soon!
We thought that the primary and secondary mirrors were a little dirty and they were, so we went through a cleaning cycle.
1) Marked the mounting position points with a marker and then removed the mirrors
2) rinsed, with the mirror at a high angle, under tap water for a minute (no compressed air available, so skipped that step).
3) with a mix of warm tap water and one drop of dishsoap, dragged wet cottonballs across the surface, from the centre to the outside edge, under their own weight.
4) rinsed again, checking for flow obstructions indicating a spec still on the surface.
5) more attention to he problem areas, sometimes with the slightest of actual pressure on the cottonball on the mirror surface.
6) another tap water rinse
7) a distilled water rinse
8) a 70% isopropyl alcohol rinse (probably will use 90%+ next time… the alcohol evaporated and left behind a lot of small water drops to evaporate).

9) drying with the mirror in an upright position.
10) remounting in the same orientation

The secondary mirror was not nearly so bad but it too was subject to the same process.
In the end, the mirror was a lot cleaner than before, which will help to improve the contrast