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AT12 RC modification and cleaning

It has already been two years since the Astrotech 12'' RC became the workhorse of Asteria observatory. It has already logged tens of hours of imaging during that time, specifically close to 150 hours. They say you're not supposed to clean the optics at all if possible, due to the thin aluminum coating that may be affected. However there came a point where I could see a layer of gunk caked on the mirror's surface, which would eventually start to affect performance by lowering the mirror's reflectivity. I think being located in the woods with all the pollen around expedited the need for a cleaning.

I finally got my nerve up to tackle this project after watching Gary Honis's excellent video on modifying the AT12, which includes the cleaning steps.

The video is very detailed and covers everything very well. It set the expectation, and by the time I was done watching, I gained the confidence needed to tackle the project. Therefore a big thanks goes out to Gary for his very informative video. Here is a photo timeline of the project:

August 11, 2018

Telescope disassembly & mirror cleaning

Before listing the steps, my first impression was what a high quality build this instrument has to the point where taking everything apart was really straight forward and predictable. Also my goal was to put everything back in the same exact position. I therefore used masking tape to mark the orientation of the various components.

1. Remove the focuser assembly and focuser adjustment ring

2. Remove the screws around the mirror cell and remove the tube assembly along with the secondary mirror and spider

3. Remove the baffle tube

4. Remove the primary collimation screws that hold the mirror cell to the back of the scope

5. Remove the safety clips around the mirror

6. Removed the rubber O-ring from the center of the mirror cell.

7. Used fishing line to break the RTV glue holding the mirror to the cell on the sides

8. Carefully pried along the back to detach the mirror from the cell, held down by glued cork pads.

9. Cleaned the mirror as follows:

a. Laid the mirror on a flat water proof surface

b. Poured distilled water to cover the surface and let it sit a few minutes

c. Used the weight of cotton balls to gently clean the surface

d. Rinsed with more distilled water

e. Removed water droplets using a blower until completely dry