The making of 26 inch Cassegrain - 11, secondary mirror done

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

The making of 26 inch Cassegrain - 11, secondary mirror done

文章 Chanlunlun » 週一 13 10月, 2014 16:46

Dear ATMers,

While it took more than a year to finish the 26 inch primary mirror, it took only one day to complete the secondary convex mirror. Our students are really exhausted in grinding, polishing and figuring the primary mirror and hence the secondary mirror was done by me solo.

The secondary mirror of a Cassegrain telescope is convex and hyperbolic in shape. I have polished the mirror but do not have a chance to put it into optical test. There is no practical shop test for a hyperbolic convex mirror except star test. Hence the figuring of the secondary will not be carried out until the finishing of all mechanical parts of the telescope.

The diameter of the secondary mirror is nearly 10 inches, already bigger than some primary mirrors in amateur telescopes.

Best regards
Chan Yuk Lun
13 Oct 2014
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23.jpg
The polished secondary mirror, its diameter is about 10 inches.
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最後由 Chanlunlun 於 週一 13 10月, 2014 21:23 編輯,總共編輯了 1 次。

Patshek
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註冊時間: 週四 11 3月, 2004 17:31
來自: HKU AC48

文章 Patshek » 週一 13 10月, 2014 21:01

There is sophisticated mirror cell for large primary mirror.

However, is there any mirror cell that is designed for secondary? What kind of design will be used on your secondary which is as large as primary?

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

文章 Chanlunlun » 週一 13 10月, 2014 21:21

Patshek 寫:There is sophisticated mirror cell for large primary mirror.

However, is there any mirror cell that is designed for secondary? What kind of design will be used on your secondary which is as large as primary?
The primary mirror will be seated on a 27 points floatation cell.

The secondary will be installed on six point fixed mirror cell. The secondary mirror works quite unlike the primary - its surface always face downward and so theweight of the mirror always acts away from the mirror cell, just contraray to the primary mirror.

Hence the secondary mirror cell could be made in a simpler fashion.

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Eddy So
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註冊時間: 週四 04 12月, 2008 22:35
來自: 中男海

文章 Eddy So » 週一 13 10月, 2014 23:19

[Good Job] [Good Job] [Good Job]

bbsdma
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註冊時間: 週一 19 1月, 2009 19:56

Re: The making of 26 inch Cassegrain - 11, secondary mirror

文章 bbsdma » 週二 14 10月, 2014 12:46

Chanlunlun 寫:Dear ATMers,

While it took more than a year to finish the 26 inch primary mirror, it took only one day to complete the secondary convex mirror. Our students are really exhausted in grinding, polishing and figuring the primary mirror and hence the secondary mirror was done by me solo.

The secondary mirror of a Cassegrain telescope is convex and hyperbolic in shape. I have polished the mirror but do not have a chance to put it into optical test. There is no practical shop test for a hyperbolic convex mirror except star test. Hence the figuring of the secondary will not be carried out until the finishing of all mechanical parts of the telescope.

The diameter of the secondary mirror is nearly 10 inches, already bigger than some primary mirrors in amateur telescopes.

Best regards
Chan Yuk Lun
13 Oct 2014
[Good Job] [Good Job] [Good Job]
這樣是否說明project轉成Classic Cassegrain?

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

Re: The making of 26 inch Cassegrain - 11, secondary mirror

文章 Chanlunlun » 週二 14 10月, 2014 15:16

bbsdma 寫:
Chanlunlun 寫:Dear ATMers,

While it took more than a year to finish the 26 inch primary mirror, it took only one day to complete the secondary convex mirror. Our students are really exhausted in grinding, polishing and figuring the primary mirror and hence the secondary mirror was done by me solo.

The secondary mirror of a Cassegrain telescope is convex and hyperbolic in shape. I have polished the mirror but do not have a chance to put it into optical test. There is no practical shop test for a hyperbolic convex mirror except star test. Hence the figuring of the secondary will not be carried out until the finishing of all mechanical parts of the telescope.

The diameter of the secondary mirror is nearly 10 inches, already bigger than some primary mirrors in amateur telescopes.

Best regards
Chan Yuk Lun
13 Oct 2014
[Good Job] [Good Job] [Good Job]
這樣是否說明project轉成Classic Cassegrain?
Yes you are correct.

The telescope will become a classical Cassegrain.

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Carl Chan
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文章: 653
註冊時間: 週一 27 10月, 2003 19:42
來自: 中國香港

文章 Carl Chan » 週二 14 10月, 2014 20:04

You are Clark Chan! [Good Job] [Good Job] [Good Job] [Good Job] [Good Job]

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

文章 Chanlunlun » 週三 15 10月, 2014 08:44

Carl Chan 寫:You are Clark Chan! [Good Job] [Good Job] [Good Job] [Good Job] [Good Job]
Carl, thanks for your flattering.

I can't be, and will never be, in any match with Clark.

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wtyu21
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註冊時間: 週三 30 5月, 2007 04:18
來自: HKCHN

文章 wtyu21 » 週四 25 12月, 2014 21:43

Carl Chan 寫:You are Clark Chan! [Good Job] [Good Job] [Good Job] [Good Job] [Good Job]
雖不是也接近(克拉克製鏡大師)啦~鏡神嘛~ :wink: :mrgreen: :mrgreen: :mrgreen: :mrgreen:

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kingyo
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註冊時間: 週二 28 8月, 2012 23:52
來自: Rosette
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文章 kingyo » 週四 25 12月, 2014 23:41

想問下你通常用邊間廠幫你鍍鋁?

謝謝

金魚

Chanlunlun
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文章: 3834
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文章 Chanlunlun » 週三 31 12月, 2014 23:34

kingyo 寫:想問下你通常用邊間廠幫你鍍鋁?

謝謝

金魚
Primary mirror will be coated by silver at school.

Sevondary mirror will be coated by ZhiTung - aluminium + quartz overcoat.

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