土法製造 null 試鏡法儀器---( 1 )
土法製造 null 試鏡法儀器---( 1 )
3月27日星期六, 由 Subaru 和 Wah 負責設計的 null 試鏡器正式組合和運作.
當晚適逢 Passerby-B 和 Leicaeddy 探訪農莊, 所以也幫手setup這土法試鏡器.
由一枝激光筆做光源,放在10"拋物面(卡式)焦點製造平行光,
再用光柵或刀片放在折射鏡後焦點前後不同位置,影像側投影在一磨沙紙上,再用數碼相機拍攝成像.
因為設備原始,多數過程要同時由三四位同好幫手.
雖然操作上有些不協調,但大家都合作愉快,尤其是見到笫一個光柵像時,大家都顯得非常興奮.
Wongsir
30-3-2004
擺放光源至主鏡半徑高度
調校激光源方向
測度平行光位置
當晚適逢 Passerby-B 和 Leicaeddy 探訪農莊, 所以也幫手setup這土法試鏡器.
由一枝激光筆做光源,放在10"拋物面(卡式)焦點製造平行光,
再用光柵或刀片放在折射鏡後焦點前後不同位置,影像側投影在一磨沙紙上,再用數碼相機拍攝成像.
因為設備原始,多數過程要同時由三四位同好幫手.
雖然操作上有些不協調,但大家都合作愉快,尤其是見到笫一個光柵像時,大家都顯得非常興奮.
Wongsir
30-3-2004
擺放光源至主鏡半徑高度
調校激光源方向
測度平行光位置
最後由 Wongsir 於 週四 17 3月, 2016 16:50 編輯,總共編輯了 3 次。
我在網上找到的:
The Foucault knife edge test is a null test for a spherical mirror at radius.
Any error visible is a defect in the wavefront being tested. A null means zero or nothing to measure. It is possible to produce a quality spherical mirror which can be used in turn to null a paraboloid. As before a visible error is a defect in the paraboloid surface and thus the wavefront undergoing the knife edge test. Since both mirrors are used at foci whereby they have spherical aberration, a null is produced when those sphericals cancel. The author has used the test for more than 25 years and presented in a article in Telescope Making #11 and followed by Ed Jones in the July 1992 issue of Sky & Telescope. What is now being presented is a update of my experience in using the test.
http://zebu.uoregon.edu/~mbartels/dnld/waineo96.html
The Foucault knife edge test is a null test for a spherical mirror at radius.
Any error visible is a defect in the wavefront being tested. A null means zero or nothing to measure. It is possible to produce a quality spherical mirror which can be used in turn to null a paraboloid. As before a visible error is a defect in the paraboloid surface and thus the wavefront undergoing the knife edge test. Since both mirrors are used at foci whereby they have spherical aberration, a null is produced when those sphericals cancel. The author has used the test for more than 25 years and presented in a article in Telescope Making #11 and followed by Ed Jones in the July 1992 issue of Sky & Telescope. What is now being presented is a update of my experience in using the test.
http://zebu.uoregon.edu/~mbartels/dnld/waineo96.html
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- 夸克星
- 文章: 3847
- 註冊時間: 週四 09 10月, 2003 21:06
Dear ATMs,mimi 寫:我在網上找到的:
The Foucault knife edge test is a null test for a spherical mirror at radius.
Any error visible is a defect in the wavefront being tested. A null means zero or nothing to measure. It is possible to produce a quality spherical mirror which can be used in turn to null a paraboloid. As before a visible error is a defect in the paraboloid surface and thus the wavefront undergoing the knife edge test. Since both mirrors are used at foci whereby they have spherical aberration, a null is produced when those sphericals cancel. The author has used the test for more than 25 years and presented in a article in Telescope Making #11 and followed by Ed Jones in the July 1992 issue of Sky & Telescope. What is now being presented is a update of my experience in using the test.
http://zebu.uoregon.edu/~mbartels/dnld/waineo96.html
Such test is called a Waineo test. It use a spherical mirror to introduce just the right amount of spherical aberration before light striking to the paraboloid under test. This test has a very big disadvantage - we need a big and good spherical mirror in advance to produce a big enough light cone to the parabola under test. If you areplanning a 24 inch mirrro you have to make a spherical mirror of at LEAST 20 INCH IN ADVANCE.
The accuracy obtained is no better than a Dall null test, however. It is of course worse than an Offner null test.
This test, as the same as Dall null test, cannot handle mirror bigger than 16 inch and faster than f/4.
Best regards
Chan Yuk Lun
一分錢, 一分貨. 不過支鏡還未到完美地步, 索價始終是高了一點.Wongsir 寫:Subaru,
你用 null test 測試 三枝廠制鏡:astro60,fs60c和c102的報告原來寫在廠制儀器的論鏡主題內.
好似高橋枝鏡 fs60c 正的呢!
等著你色差和軸外像差測試報告.
Wongsir
31-3-2004
已經諗咗軸向色差點度, 但側向色差還要睇睇點先度得準; 至於軸外像差方面就要用多一點時間及器材先做到. 近來工作開始忙, 可能要等一等先有時間攪.
其實農莊引入了null test之後, Wongsir的弟子要磨得比廠更靚嘅鏡已經不再是難事. 晚輩期望日後有更多高精度自製鏡出自本港天文同好. Wongsir不妨考慮埋引入精度高一倍的autocollimation test, 到時廠鏡更加無所鈍型.
Subaru,Subaru 寫:一分錢, 一分貨. 不過支鏡還未到完美地步, 索價始終是高了一點.
已經諗咗軸向色差點度, 但側向色差還要睇睇點先度得準; 至於軸外像差方面就要用多一點時間及器材先做到. 近來工作開始忙, 可能要等一等先有時間攪.
其實農莊引入了null test之後, Wongsir的弟子要磨得比廠更靚嘅鏡已經不再是難事. 晚輩期望日後有更多高精度自製鏡出自本港天文同好. Wongsir不妨考慮埋引入精度高一倍的autocollimation test, 到時廠鏡更加無所鈍型.
Can you tell me more about autocollimation test and its setup?
Wongsir
31-3-2004
最後由 Wongsir 於 週三 31 3月, 2004 23:49 編輯,總共編輯了 1 次。
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