Polishing
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Polishing the mirror

Tools: new matricx, hot pitch (calofonium and tar),cerium-oxide  (Ce2O3),a piece of wood for making the channels on the matrix(a knife can be used as well). The polishing is the last step in making the primary mirror; with polishing it is achieved the final reflectiveness. It is done for about 3-4 hours, and if  there are some problems it has to be done even longer. We have already found some mistakes after a half an hour of work. In one case the best polished were the edges of the mirror,in the other case the best polished were some concentric zones on the mirror and in the third case everything was OK. Later we came to the con conclusion that the planes on which we put the matrix were wet so they changed the shape of the wooden matrix. We decided to make new matrix of the new material which isn't so vulnerable by the wetness as wood is. We made new matrix-two of them were made of wood (painted

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with the protective paint) and one was of aluminium. This time we were using softer pitch than the last time. After we made the channels on the matrix we started to polish. Fortunately, we noticed that the mistakes are getting smaller. In spite of that we should polish for 3-4 hours more.

’96

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