Dear ATMers,
After 2 hours of 1/3 center to center stroke by #40 grits the surface of the mirror turned into a perfect sphere. After another 2 hours of fine grinding by #80 grits, the first stage of fine grinding was finished.
Finally an additional of 1.5 hours of #180 grit concluded today’s operation.
There leaves #320, 600 and 1200 grits to go. At the moment the focal length of the mirror is at 74 inches, or at f/4.6, according to measurement by a Vernier caliper. ( Sagitta measurement )
Although at extreme high temperature within very humid environment, ( no air con at our little optical shop ) the progress was kept at satisfactory speed.
Best regards
Chan Yuk Lun
23 June 2009
Making of 16 inch PTC telescope - 2, #180 finished
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Chanlunlun
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- 文章: 3847
- 註冊時間: 週四 09 10月, 2003 21:06
Making of 16 inch PTC telescope - 2, #180 finished
- 附加檔案
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- The starting of #80 fine grinding. A big hole at center indicates that the mirror and tool are not matching at central portion. Fine grinding for a little more time will eliminate this.
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![[Good Job]](./images/smilies/onion_d5f02ecd.gif "Good Job")
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Chanlunlun
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- 文章: 3847
- 註冊時間: 週四 09 10月, 2003 21:06
Yes, yes , yes !! I am trying very very hard now. All people in school are curoius what I am doing now. It seems to them that I am busy at constructing a wooden UFO !
最後由 Chanlunlun 於 週三 24 6月, 2009 16:39 編輯，總共編輯了 1 次。
即北潭涌：bbsdma 寫:請教前輩、學長：
PTC是什么縮寫? Google不出答案來
http://bus.mapbar.com/hongkong/poi/5CN6zj6sC
http://zh.wikipedia.org/wiki/%E5%8C%97% ... D%E6%B6%8C
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Chanlunlun
- 夸克星
- 文章: 3847
- 註冊時間: 週四 09 10月, 2003 21:06
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Moonwalker
- 超新星
- 文章: 6
- 註冊時間: 週四 02 8月, 2007 13:13
Dear Mr Chan,
For small mirrors, we can use bubble and pencil to test whether the surface curvature is close to spherical, since we can use 1:1 for tools and mirror. However, for the large ones, we are more likely to use small tool during fabrication. So how can we test the surface curvature during earlier stages?
Regards,
Moonwalker
For small mirrors, we can use bubble and pencil to test whether the surface curvature is close to spherical, since we can use 1:1 for tools and mirror. However, for the large ones, we are more likely to use small tool during fabrication. So how can we test the surface curvature during earlier stages?
Regards,
Moonwalker
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Chanlunlun
- 夸克星
- 文章: 3847
- 註冊時間: 週四 09 10月, 2003 21:06
Use a spherometer.Moonwalker 寫:Dear Mr Chan,
For small mirrors, we can use bubble and pencil to test whether the surface curvature is close to spherical, since we can use 1:1 for tools and mirror. However, for the large ones, we are more likely to use small tool during fabrication. So how can we test the surface curvature during earlier stages?
Regards,
Moonwalker
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