The arrival of 24 inch mirror blanks.

自製天文望遠鏡 牛頓望遠鏡 杜蘇式 卡式 設計和磨鏡方法<br>
佛科試鏡法 佛科刀片儀 光柵試鏡法 光柵片
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Chanlunlun
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註冊時間: 週四 09 10月, 2003 21:06

The arrival of 24 inch mirror blanks.

文章 Chanlunlun » 週五 16 1月, 2004 17:22

Dear ATMs,

The 24 inch mirror blanks have arrived. Both the mirror and the tool are of thickness 1 inch, diameter 24 inches.

The focal length of the mirror has been decided to be at 84 inches. i.e. at a focal ratio of 3.5. We also decided to grind and polish the mirror by a full size tool and full size lap. The figuring of the mirror will be done by a small lap, only 3.5" in diameter.

The method of testing the prarboloid has not yet been fixed. Any one who has any idea about testing of big mirror please do not hesitate to offer your opinion. You are always welcome.

Hofefully the telescope will be finished before June this year.

Best regards

Chan Yuk Lun
16-1-2003
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Img_5526a.jpg
Mr. Sodium and the 24 inch mirror blank. Mr.Sodium will be one of the mirror grinding team for this 24 inch telescope project.
Img_5526a.jpg (65.64 KiB) 已瀏覽 12796 次

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Subaru
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文章 Subaru » 週五 16 1月, 2004 17:28

8) Sodium會唔會用NaOH溶感d玻璃先, 唔洗磨得噤辛苦呢? (千其唔好試, 講笑炸).

用full size tool磨完之後塊主鏡會唔會好薄?

真係好想有機會跟陳sir出去用支24"睇deepsky.

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豆豸苗
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文章 豆豸苗 » 週五 16 1月, 2004 17:33

wa!!! Sodium 好威呀~~~ ^^

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Subaru
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文章 Subaru » 週五 16 1月, 2004 21:55

豆豸苗 寫:wa!!! Sodium 好威呀~~~ ^^
大有前途, 大有前途.

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Wongsir
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文章 Wongsir » 週五 16 1月, 2004 22:14

嘩,成張抬咁大,
簡直創舉.
sodium,
記得俾心記跟陳sir學野o阿!

Wongsir
16-1-2004

Chanlunlun
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文章 Chanlunlun » 週五 16 1月, 2004 22:45

Subaru 寫:8)

用full size tool磨完之後塊主鏡會唔會好薄?
Dear Mr. Subaru,

For grinding and polishing of big mirror, a full size tool is a must. While a sub-diameter tool can also do the job quite well, it suffers from drawback of low efficiency.

You may have a lot of labour saved when using full size tool. All we need to do is to close monitor the edge thickness during rough grinding.The goal is to keep the edge as thick as possible. As experience from the 20 mirror inch tells, we can retain 100% edge thickness even with a full size tool.

Best regards

Chan Yuk Lun
16-1-2004

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david_kmng
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文章 david_kmng » 週五 16 1月, 2004 23:02

Amazing!

I would like to learn and grind a 20" mirror. I did a 4" mirror a long time ago!

Regards,
David

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WenXP
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文章 WenXP » 週六 17 1月, 2004 04:44

請問鏡神所指的 full size tool 將是用何物料所製?

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

文章 Chanlunlun » 週六 17 1月, 2004 09:34

WenXP 寫:請問鏡神所指的 full size tool 將是用何物料所製?
Dear Mr. WenXP

We have ordered two glass disks of 24 inch diameter and thickness 1 inch. One will be the mirror and one will be the tool. So the tool is exactlt the same as the mirror blank. It is a full size tool.

Best regards

Chan Yuk Lun
17-1-2004

oldsaltfish
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註冊時間: 週五 03 10月, 2003 08:32

文章 oldsaltfish » 週一 26 1月, 2004 12:08

I am afraid the thickness is not enough

Chanlunlun
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文章 Chanlunlun » 週四 05 2月, 2004 13:30

oldsaltfish 寫:I am afraid the thickness is not enough


Dear Mr. OldSaltFish

This is also my worry. However as analysised by finite element method, the deformation of the mirror is verY very small even at 24:1 thickness ratio, under a 18 point floatation cell.

So we just go for it.

Best regard

Chan Yuk Lun
5-2-2004

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