ATM Buddy — Mobile Tools for Amateur Telescope Makers

Base quantity is 150ml distilled water + 1.6g silver nitrate.
Other quantities are derived from that.
Recipe from Gerhard S. on Cloudy Nights

BOM for a session

The chemicals

Step 0

Calibrate bottles

Calibrate Bottle 1 and Bottle 2 with water, ensuring that the same quantity of water is sprayed with 100 sprays.

Step 1

Prepare the solutions

Base quantity (ml):

Solution 1: 1.6g silver nitrate + 150ml distilled water

Solution 2: 2.5g sodium hydroxide + 150ml distilled water

Solution 3: 12g glucose + 300ml distilled water

Bottle 1 is the mixed solution according to below instructions.

Bottle 2 contains the sugar Solution 3

Step 2

Mixing of silver solution

(becomes Bottle 1)

1 : Pour about 100ml ml of Solution 1 into a mixing bowl.
2 : Add a few drops of ammonia solution (25% dilution)
3 : Add all of Solution 2
4 : Add the rest of Solution 1 (the solution will turn brown)
5 : Carefully add ammonia solution drop by drop while stirring until a transparent, slightly brownish solution is obtained.

The cleaning and spraying

Clean the mirror

Use chalk precipitate in distilled/demin water on small cotton balls. Change often and start with thick sauce, thinning it progressively. The center will clean fast but the edge and chamfer need a LOT of time.

Rough guideline : (diameter_in_mm/15)^1.4 = time.
Yes, that is an advice of 1h40 for a 400mm mirror.

Rinse with demin water and if possible, high pressure.

Create optical pieces in the Hardware tab to quickly load their dimensions here.

Mirror diameter in mm:

Cleaning time : 0h25m

Spray the mirror

Spray the mirror with both sprays, ensuring that they mix on the surface. You will see a faint blue film appear first.
Then it will turn yellowish. If you see dark brown or black streaks, this means your cleaning wasn't thorough enough.
A thin coating is preferable to a thick one and it should still be a tad transparent at the end.

Dry & store

Immediately dry with a hot air gun and store in an airtight box with dessicant packs, or better, silver protector felt. Silver protector felt is felt impregnated with tiny silver particles that are there to react with oxydants first and protect your coating.