Wednesday, January 28, 2009

Cleaning your telescope's primary mirror.

Okay here is the technique I use for cleaning my primary mirror. In the 4 years I have owned my scope, I have cleaned the primary and secondary mirror twice. Since I live in the desert my scope picks up alot of dust and I do hold off as long as possible before I do this. My mirror costs $850.00 to replace or $250.00 to recoat so I don't take cleaning it lightly. I have cleaned over 20 primary mirrors and have not had any problems with this technique. Here is the formula for the cleaning solution.....
2 cups distilled water
1/8th cup of 90% Isopropyl Alcohol
3 small drops of clear dishwashing liquid
I gallon of distilled water for rinsing.
1 bag of sterile cotton balls
You can get distilled water at the grocery store for around a buck a gallon.
Add the 2 cups of distilled water into a bowl, then add the alcohol, then the dishwashing soap (in that order) then mix with a spoon. you don't want the soap to foam up your mixture.
Remove the primary mirror from the mirror cell and blow off the dust with your breath. I don't use canned air because the propellant can damage your mirror coatings instantly. Fill your kitchen sink half full with lukewarm tap water and place the mirror in water face up and let it soak for around 10 to 20 minutes. Pour your cleaning solution in a bowl and add about 20 cotton balls into the solution. Take the mirror out and place it on a towell and keep it wet with the distilled water. Now take a soaked cotton ball from the solution and place it in the center of the mirror. Now drag the cotton ball using only its own weight (don't push down on it) to the edge of the mirror and throw the cotton ball away. Take another soaked cotton ball and do the same thing. Work your way in a circle around the mirror only pulling the cotton balls from the center to the edge. NEVER use a cotton ball twice. Always throw them away after 1 pass. After going around the entire mirror tilt the mirror up (in the sink) and rinse with the distilled water. The distilled water will mostly run off in a solid sheet . For any remaining spots of water use a paper towell folded to a small point and just barely touch it to the water droplet and it will soak it off of the mirror. That is pretty much it. Don't resort to cleaning the mirror unless it is REALLY dirty. If you end up 1 or 2 water spots don't worry about them for they will not affect your viewing at all.

1 comment:

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