24 inch mirror - 14 hrs. of parabolizing

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Chanlunlun
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註冊時間: 週四 09 10月, 2003 21:06

24 inch mirror - 14 hrs. of parabolizing

文章 Chanlunlun » 週五 26 3月, 2004 11:37

Dear ATMs,

At the end of the day we have completed 14 hours on parabolizing the mirror. What made us happy is that the mirror does show some response, but still slower than what we first estimated. Anyway we were still satisfied since at least something showed up on the mirror.

This was our third trial to make a specialize parabolization lap and this time it was a success. The lap is a 8.5 diameter with a flat piece of plywood as substrate. The pitch is rather hard to avoid sucking onto the mirror surface and thus it was rather easy to push the lap onto the mirror surface. This lap is specialize in reducing the central part of the mirror. After 3 hours of hard working on the mirror center a small hole starts to appear, as shown in the attached diagram.

What we were doing was try to reduce the radius of curvature of the central part of the mirror to suit the profile of a parabola. To do this the most efficient way was to localize the polishing to the central portion only, leaving the outer part of the mirror intact. This was why we need a small lap to do the job.

The parabolization proceed very slowly, we guess we need another 30 hours or so before the mirror can be finished.

We have a time consuming war to fight.

Best regards

Chan Yuk Lun
25-3-2004
附加檔案
deepening_center.jpg
Mr. Sodium is working hard in reducing the center of the mirror. Don』t give up, Sodium, you have a war to fight.
deepening_center.jpg (50.09 KiB) 已瀏覽 7017 次
profile_2.jpg
The mirror profile tonight. You can see that comparing to last night』s profile a central hole starts to emerge. The hole is not big enough, we need more local polishing in the central portion of mirror.
profile_2.jpg (68.35 KiB) 已瀏覽 7017 次

bandofbrother
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註冊時間: 週四 25 12月, 2003 19:38

文章 bandofbrother » 週五 26 3月, 2004 16:10

其實我有個問題關於拋光粉
就係拋光粉係咪有隻係紅色,有隻係白色????
如果係,咁佢地既分別係咩,邊隻好d

Chanlunlun
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文章: 3800
註冊時間: 週四 09 10月, 2003 21:06

文章 Chanlunlun » 週五 26 3月, 2004 16:48

bandofbrother 寫:其實我有個問題關於拋光粉
就係拋光粉係咪有隻係紅色,有隻係白色????
如果係,咁佢地既分別係咩,邊隻好d
Dear Mr. BandofBrothers,

The red one is called rouge, it is in fact iron (III) oxide. It gives an excellent polish but its speed is extremely slow. It is rarely used nowadays.

The white one is used for polishing jewelery, not suitable for optical purpose as its speed is slow while at the same time not giving a good enough polish on glass.

The brown one is Cerium Oxide, it has a very fast polishing speed and it also gives an excellent polish. It is widely used nowadays for optical polishing, include in the field of amatuer telescope making.

Hopefully your question is well answered.

Best regards

Chan Yuk Lun

bandofbrother
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文章: 183
註冊時間: 週四 25 12月, 2003 19:38

文章 bandofbrother » 週五 26 3月, 2004 19:48

唔該曬chan lun lun

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