In the first picture, the pits came from the rough grinding or "hogging out"the mirror, which is the first stage of making a telescope mirror. We hogged out the mirror using a 60 grit silicon carbide.
The second stage is fine grinding.After finishing with the 60 grit, we started using a 120 grit, also a silicon carbide. Fine grinding is taking the pits out from when we did rough grinding. After the first charge of 120 grit half of the pits were gone. At the end of a 120 grit, there were 6 pits left. We marked these pits on the back side of the mirror, to make the back rougher and to cheek on our progress.
We then went to the 25 grit White Aluminium Oxide. We crossed-hatched many times to make sure we still had good contact when the lines rubbed off quickly. We had 1 pit left. After this we went to a 15 grit White Aluminium Oxide. We now have no large pits when the mirror is viewed through a bright light source!! At the end of the 9 White Aluminium Oxide, we had 1 very small scratch which we will polish out. The mirror is very smooth, but has a frosted look. The frosted look comes from the many tiny pits. To get rid of this frosted look, just quirt water on the mirror.
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