Yesterday was the first day of my 5-day telescope making process. I am under the process of making a 4-inch telescope. The first and the longest process of making the telescope is grinding the 4-inch mirror over another doubly-thick 4-inch glass tool. The process, as I realized after starting to follow it, requires much more strength and endurance than I thought earlier.
The process uses silicon carbide (second toughest material on Earth, ranking after diamond) solution for grinding the mirror. There are six particle sizes of the 'grit' (silicon carbide mixture) to complete the full grinding process. I completed sizes 320 and started 400 (larger the number, finer the particles).
The process involves a huge flat drain bowl with a turn-able wooden platform in its center and three small adjustable rectangular metal pieces at 120 degrees to each other screwed to the platform. The glass tool is tightened between these three pieces so that the position of the tool remains intact the way it is required. A little bit of the grit is then poured over the glass tool. The grinding process then starts over it (a long and tedious process). Here it goes!:
For the first grinding process, the mirror's center is aligned over the glass tool's center. Then a scraping motion of 'away from you - then - towards you' is started; but only 20-25 complete strokes. Then, with the help of the metal pieces as markers, only the mirror has to be rotated by 120 degrees over the glass tool, and again 20-25 strokes have to be executed. Once again, the mirror has to be rotated by 120 degrees over the tool and 20-25 strokes have to be executed. This completes one revolution of the mirror. Now, the complete platform with all the other stuff over it has to be rotated by 45 degrees and the whole grinding process as above has to be continued until a 360 degree round of the platform is over. Along with this, the grit has to be replaced over and over so that the glass tool and the mirror do not stick together.
Different types of strokes took different amounts of time. The first basic scraping process was not very time-taking but by the time I started with the 400 grit, the revolutions took so long each because each stroke was a long stroke. By the time i completed 6 revolutions of the platform over the four hour session, my arms and shoulders were aching. A real tough job it is! I will be continuing this process over the next few days and will keep the blog updated!
The process uses silicon carbide (second toughest material on Earth, ranking after diamond) solution for grinding the mirror. There are six particle sizes of the 'grit' (silicon carbide mixture) to complete the full grinding process. I completed sizes 320 and started 400 (larger the number, finer the particles).
The process involves a huge flat drain bowl with a turn-able wooden platform in its center and three small adjustable rectangular metal pieces at 120 degrees to each other screwed to the platform. The glass tool is tightened between these three pieces so that the position of the tool remains intact the way it is required. A little bit of the grit is then poured over the glass tool. The grinding process then starts over it (a long and tedious process). Here it goes!:
For the first grinding process, the mirror's center is aligned over the glass tool's center. Then a scraping motion of 'away from you - then - towards you' is started; but only 20-25 complete strokes. Then, with the help of the metal pieces as markers, only the mirror has to be rotated by 120 degrees over the glass tool, and again 20-25 strokes have to be executed. Once again, the mirror has to be rotated by 120 degrees over the tool and 20-25 strokes have to be executed. This completes one revolution of the mirror. Now, the complete platform with all the other stuff over it has to be rotated by 45 degrees and the whole grinding process as above has to be continued until a 360 degree round of the platform is over. Along with this, the grit has to be replaced over and over so that the glass tool and the mirror do not stick together.
Different types of strokes took different amounts of time. The first basic scraping process was not very time-taking but by the time I started with the 400 grit, the revolutions took so long each because each stroke was a long stroke. By the time i completed 6 revolutions of the platform over the four hour session, my arms and shoulders were aching. A real tough job it is! I will be continuing this process over the next few days and will keep the blog updated!
-Suhas
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