蘇魯定先生的鏡-2

檢測望遠鏡光學部份,赤道儀機械組件,目鏡配件和拍攝器材 CCD等...
回覆文章
Chanlunlun
夸克星
文章: 3791
註冊時間: 週四 09 10月, 2003 21:06

蘇魯定先生的鏡-2

文章 Chanlunlun » 週日 02 11月, 2008 09:13

Dear Mr. So,

Sorry again for keeping you waiting. If you know how difficult it is to collect all the items for a fair star test you may probably forgive my delaying.

On 9th September 2008 a successful star test was carried out and a full evaluation of your mirror was finally concluded. Earlier shop test by Foucalt method indicated that your supplied mirror is at a surface accuracy of about 1/8 wave P.V. and with a Strehl ratio of about 0.8 . In order to verify the shop test result I deliberately made a mirror with surface accuracy of 1/17 wave , Strehl ratio of 0.92. We had chosen a night with sufficient steadiness to show up the difference of two mirrors, if any.

That night finally came. We made two telescopes as identical as possible to ensure they operate at exactly same condition ( they don’t have the same focal length , however, as I am not good enough to figure a f/5 mirror up to 1/20 wave P.V.) . Both telescope was constructed at same open frame structure with the same kind of wood. Both of them have the same batch of secondary mirror ( Astro 52 mm plate glass diagonal, same batch ). Observation were made with the same Brand eyepiece ( Takahashi LE series eyepiece. LE 5 mm for the reference mirror, LE 3.6 mm for Mr. So’s mirror ). Below are full description about the two telescopes under test :-

Mr. So’s telescope :-

1. Primary Mirror – 8 inch aperture at f/5. Smooth surface with no irregularity detected. Surface accuracy 1/8 wave P.V. Sthrel ratio : 0.82. Coating by Zhi Tong company, single surface aluminum overcoated by silicone monoxide. Siliocon monoxide coating appears to be a little too thick, central portion of mirror very slightly turned pale red.

2. Diagonal mirror – Astro 52 mm minor axis plate glass mirror. Surface accuracy : unknown. Single aluminum coating with standard silicone monoxide overcoated.

3. Eyepiece – Takahashi LE 3.6 mm making a magnification of 278 X. As a standard star test required a 320 X for evaluation this was the closest possible magnification we could obtained using a single eyepiece. We avoid using Barlow lens as it would downgrade the overall optical quality.

4. OTA – 4 column wooden frame open structure. This structure allows quick thermal equilibrium of mirror.

5. Equatorial mount :- Takahashi EM-1s with tracking motor off. All tracking was carried out by hand to avoid motor vibration affecting telescopic resolution.

6 Judge :- me, Mr. Chung HL and Mr. A/45 Lawrence.

Reference telescope :-

1. Primary Mirror :- 8 inch aperture at f /7.1. Smooth surface with a turn down edge (TDE) of width less than 1 mm. Surface accuracy 1/17 wave P.V. Sthrel ratio : 0.92. Coated by ZhiTong company, single aluminum overcoated by silicon monoxide. Silicon monoxide overcoating appeared to be too thick and central portion of mirror carried noticeable pale red color.

2. Diagonal mirror – Astro 52 mm minor axis, plate glass mirror. Surface accuracy : unknown. Single aluminum coating with standard silicone monoxide overcoated.

3. Eyepiece – Takahashi LE 5 mm making a magnification of 290 X. As a standard star test required a 320 X for evaluation this was the closest possible magnification we could obtained using a single eyepiece. we didn’t use a Barlow lens as it would downgrade the overall optical quality.

4. OTA – 4 column wooden frame open structure. This structure allows quick thermal equilibrium of mirror.

5. Equatorial mount :- Takahashi EM-1 with tracking motor off. All tracking was carried out by hand to avoid motor vibration affecting telescopic resolution.


Two targets were chosen for judgement purpose – the first quarter moon and Jupiter.

For lunar viewing both telescopes gave crisp images with very high contrast. They both performed very well at sight. However more careful inspection revealed the fact that the reference telescope gives a slightly better contrast ( although Mr So’s contrast is very high already ) and more resistance to air turbulence – it seemed that the reference telescope could resolve the finest detail more often than Mr. So’s telescope. .

If the moon surface had delivered us a delicious main course making up of high contrast detailing features then Jupiter was a splendid desert full of tell-tale observation facts. Among the four Jovian moons Ganymede and Io have visual diameter of 1.5 and 0.9 arc sec respectively and they all laid on one side of Jupiter.

The diameter of Airy disc for an 8 inch mirror is 1.4 arc second – just enough to resolve Ganymede but incapable for Io. If the mirror is good enough to beat the Rayleigh criterion Ganymede should be well resolved into a disc but Io will stay star like. This was what exactly we observed – both telescopes easily resolved Ganymede as solid disc. But Io acted quite differently between two telescopes.

In So’s telescope there was one diffraction ring surrounding Io. Although barely observable the diffraction was still there. For the reference telescope Io was just a point, no diffraction ring present. This was the difference of 0.8 and 0.92 Strehl ratio. The higher the Strehl ratio the more energy will be concentrated onto the Airy disc and less chance of detecting the diffraction ring. On a clear night I belief that both telescope will show the diffraction ring around Io, but it was just the hazy sky that cut off the intensity of the diffraction ring for 0.9 Strehl mirror making it invisible and provided an ultimate judge for a 0.9 Sthrel ratio against a 0.8.

It was a mere coincidence that Jupiter offered just the right condition for telescopic testing of 8 inch aperture. From this solid proof we may conclude that Mr So’s mirror has a Strehl ratio lower than 0.9 but close to 0.8. This transfer to a surface accuracy of about 1/8 wave P.V., compatible with the optical shop test result.

We rarely have a chance to AB test two equal aperture mirrors with 0.8 and 0.92 Strehl ratios. We may as well take this chance to draw the following conclusions :-

1. a 1/8 wave P.V. and a 1/17 wave P.V. mirror both perform excellently and difficult to tell their difference during most of the time.

2. However a 1/17 wave P.V. mirror will give a slightly higher contrast but this difference is only noticed at AB comparison.

3. On night of average seeing a 1/17 wave P.V. mirror tends to give more chance of seeing finer details than a 1/8 wave P.V. mirror.

4. It seems that a mirror with higher Strehl ratio gives a richer tonal variations and more subtle brightness levels upon high power observation of lunar surface. A lower Strehl ratio mirror tends to give more paleness on the lunar image.

Although not in the range of 1/20 wave P.V. ultra high precision, Mr’s So’s mirror is already a very nice piece of work which outperforms many commercially available items. I can hardly imagine anyone would be dissatisfied with the performance of a telescope equipped with one such nice mirror.

Indeed as an admirer of Mr So I am always ready to hear and learn from you and undoubtedly you are among one of the top man in the circle of ATMing.

Sorry that I have postponed submitting this report for such a long time. Sorry again that I have written in English – I have to because I am weak ( actually, don’t know how to ) in inputting Chinese into a computer.


Best regards
Chan Yuk Lun
14th September 2008.
附加檔案
soo_5.JPG
Upper drawing is what we had observed in Mr. So’s telescope. Io is at the far right. Notice the diffraction ring around Io. Below is the same observed by reference telescope – Io was just star like with no diffraction ring. Both telescopes resolved Ganym
soo_5.JPG (5.73 KiB) 已瀏覽 29248 次
soo_2.JPG
Reference mirror, also coated by ZhiTong
soo_2.JPG (52.34 KiB) 已瀏覽 29248 次
soo_1.JPG
Mr. So’s mirror , coated by ZhiTong
soo_1.JPG (55.1 KiB) 已瀏覽 29248 次

Chanlunlun
夸克星
文章: 3791
註冊時間: 週四 09 10月, 2003 21:06

文章 Chanlunlun » 週日 02 11月, 2008 09:15

More pictures........
附加檔案
soo_3.JPG
Reference telescope
soo_3.JPG (62.19 KiB) 已瀏覽 29240 次
soo_4.JPG
Mr. So’s telescope.
soo_4.JPG (49.7 KiB) 已瀏覽 29240 次

頭像
Tarepanda
夸克星
文章: 9315
註冊時間: 週一 08 11月, 2004 13:28
來自: 香港

文章 Tarepanda » 週日 02 11月, 2008 12:29

終於有報告出來了
看來下了一翻苦工
不知另一位高手-BJ大風的鏡子的平測報告何時出來

Chanlunlun
夸克星
文章: 3791
註冊時間: 週四 09 10月, 2003 21:06

文章 Chanlunlun » 週日 02 11月, 2008 14:52

Tarepanda 寫:終於有報告出來了
看來下了一翻苦工
不知另一位高手-BJ大風的鏡子的平測報告何時出來
Dear Mr. Panda,

Unfortunately I am quite involved at the moment. Several projects are on my hand and they all have to be carried out simultaneously - 30 inch telescope mechanical construction, 16 inch RCOS robotic observatory starting up and 20 inch telescope upgrading for XingLong trip.

BJDF mirror needs to wait for a while. Will keep everybody informed when results emerged.

Best regards
Chan Yuk Lun

苏鲁锭
主序星
文章: 280
註冊時間: 週六 19 8月, 2006 21:34

文章 苏鲁锭 » 週日 02 11月, 2008 20:06

虽然我一点也没有看懂英文。但是我还是真诚的感谢陈先生做辛苦的对比检测。
谢谢!!

苏鲁锭
主序星
文章: 280
註冊時間: 週六 19 8月, 2006 21:34

文章 苏鲁锭 » 週日 02 11月, 2008 20:17

有很多检测我没有办法拍下来。
我看过:
http://www.hkastroforum.net/viewtopic.p ... &start=135


第十页的第十二楼。
“。。。。。。。。 最震撼人心的時刻發生了!!!!
佛科像的鏡片是完美無瑕, 完完全全地平整, 刀口在焦點切下時, 整個鏡面同時間均勻地暗下來, 除了受大氣氣流影響之外, 鏡面基本上是見不到有光暗凹凸之處!!!!! 。。。。。。。。。。。。。”
这个我可以做到。
所不同的是我是用50微米针孔。他们用的是天然星光。如果我的针孔小到3-5微米。就好了。
陈先生有时间试一试。

頭像
Tarepanda
夸克星
文章: 9315
註冊時間: 週一 08 11月, 2004 13:28
來自: 香港

文章 Tarepanda » 週日 02 11月, 2008 20:29

Chanlunlun 寫:
Tarepanda 寫:終於有報告出來了
看來下了一翻苦工
不知另一位高手-BJ大風的鏡子的平測報告何時出來
Dear Mr. Panda,

Unfortunately I am quite involved at the moment. Several projects are on my hand and they all have to be carried out simultaneously - 30 inch telescope mechanical construction, 16 inch RCOS robotic observatory starting up and 20 inch telescope upgrading for XingLong trip.

BJDF mirror needs to wait for a while. Will keep everybody informed when results emerged.

Best regards
Chan Yuk Lun
難怪近來都不見你在水口出現
慢慢來,不急的 :D

頭像
梅西爾
夸克星
文章: 3453
註冊時間: 週四 27 3月, 2008 14:04

文章 梅西爾 » 週一 03 11月, 2008 18:40

請問那幅soo_5的圖是畫出來的嗎?

TONGKW
中子星
文章: 1923
註冊時間: 週二 13 9月, 2005 14:35
來自: Hong Kong

文章 TONGKW » 週一 03 11月, 2008 21:59

粗略翻譯

陳先生測試國內蘇先生精磨的8英吋口徑反射鏡,報告 No. 2

致:蘇先生,

再次抱歉讓您久等了。如果你知道是多麼困難去收集所有項目來進行一個公正的星點檢驗你可能原諒我的拖延。

在2008年9月9日終於成功地進行了星點檢驗及全面評估您的反射鏡。早些時候在室內進行的傅科測試顯示您提供的反射鏡表面精度約1 / 8波P.V.並有Strehl Ratio約0.8 。為了驗證這結果我特意磨製了壹塊表面精度達1 / 17波及 Strehl Ratio 0.92 的反射鏡。我們選擇了一個有足夠的穩定性的晚上來顯出這2塊反射鏡的差異,如果有的話。

那個晚上終於來臨。我們造了2台盡可能完全相同的望遠鏡以確保它們運行在相同條件下運作(它們並不具有相同的焦距,是因我沒有足夠功力磨製焦比 f/5的反射鏡其精度達1 / 20波P.V.) 。這2台望遠鏡都構建成同一款開放式框架與及採用相同的木材。它們都採用相同批次的副鏡(Astro 52 mm平玻璃對角,同批次) 。觀測採用同一品牌目鏡(高橋 LE系列目鏡。參考反射鏡採用高橋 LE 5 mm目鏡,蘇先生的反射鏡採用高橋 LE 3.6 mm目鏡) 。下面是充分說明對兩台望遠鏡進行的測試: -

蘇先生的望遠鏡: -
1 。主鏡,8英寸口徑,焦比f/5 。表面光滑,沒有發現異常。表面精度1 / 8波P.V. Strehl Ratio 0.82 。智通公司的鍍鋁再加矽一氧化碳。 這矽一氧化碳表層似乎有點過於厚,鏡子中央部分有非常輕微淺紅色。
2 。副鏡,Astro 52 mm短軸,平玻璃反射鏡。表面精度:不知。單層鍍鋁與標準矽一氧化碳。
3 。目鏡,高橋LE 3.6 mm得出放大率278x,作為一個標準的星點檢驗需要放大率320x,這是盡可能使用單一目鏡達至的放大率。我們盡量避免使用巴洛透鏡,因為它會降低整體光學質量。
4 。鏡筒,4條支拄加木框開放的結構。這種結構可讓主鏡達至快速熱平衡。
5 。赤道儀,高橋 EM1-s,將電馬達關掉改用手動跟踪,以避免馬達的振動影響望遠鏡的解像力。
6 。評判人仕,我本人,H L Chung 先生及A /45 Lawrance 先生。

參考望遠鏡: -
1 。主鏡,8英寸口徑,焦比 f/7.1。表面光滑有低邊寬度不到1mm。表面精度1 / 17波P.V. Strehl Ratio 0.92 。智通公司的鍍鋁再加矽一氧化碳。 這矽一氧化碳表層似乎有點過於厚,鏡子中央部分有非常輕微淺紅色。
2 。副鏡,Astro 52 mm短軸,平玻璃反射鏡。表面精度:不知。單層鍍鋁與標準矽一氧化碳。
3 。目鏡,高橋LE 5 mm得出放大率290x,作為一個標準的星點檢驗需要放大率320x,這是盡可能使用單一目鏡達至的放大率。我們盡量避免使用巴洛透鏡,因為它會降低整體光學質量。
4 。鏡筒,4條支拄加木框開放的結構。這種結構可讓主鏡達至快速熱平衡。
5 。赤道儀,高橋 EM1-s,將電馬達關掉改用手動跟踪,以避免馬達的振動影響望遠鏡的解像力。

選擇2個觀測目標作為判斷,第1個是上弦月及第2個是木星。
這2台望遠鏡在觀測月亮表面時都有清晰的影像及非常高的反差。它們都表現非常出色。然而在更仔細的觀測下發現一個事實,即參考望遠鏡提供了稍微好一點的反差(雖然蘇先生的反差已經非常之高)和可以更多的抵抗空氣湍流,似乎這台參考望遠鏡在很多時得出的解像力多於蘇先生的。

如果月球表面為我們提供了”美味的主菜”這是說高反差及詳細特徵,然後木星就是一個”燦爛的沙漠”充滿了可觀測的事實。在四個木星的衛星中,木衛三(Ganymede)和木衛一(Io)具有視覺直徑為1.5弧秒和0.9弧秒,都在木星的一邊。

一個8英寸口徑反射鏡的艾里班直徑是為1.4弧秒,這僅足夠分辦木衛三,但不足夠分辦木衛一。如果反射鏡的質素是優於瑞利判據,木衛三會被分辦為一個光盤,但木衛仍只被分辦為一個星點。一如所料,這2台都很容易地將木衛三分辦為一個光盤。但木衛一在2台望遠鏡觀測之下有截然不同的結果。

在蘇先生的望遠鏡觀測之下有一個衍射環包圍着木衛一。雖然只是勉強可以觀察得到這衍射是仍然存在。在參考望遠鏡觀測之下木衛一只是一個星點而沒有衍射環。這就是 Strehl Ratio 0.8和 Strehl Ratio 0.92 StrehlRatio 比較下的差別。越高的Strehl Ratio 會將更多的能量集中到艾里班因而減小可以觀測得到衍射環的可能性。維如在一個晴朗的晚上,我相信這2台望遠鏡都會觀測到衍射環包圍着木衛一,但由於朦朧的天空減小衍射環的强度使令Strehl Ratio 0.9的反射鏡看不見它,這提供了Strehl Ratio 0.9 與Strehl Ratio 0.8 比較之下最終的判斷
這只是一個巧合木星剛好提供合適的條件來測試8英寸口徑。從這一堅實的證據,我們可以得出的結論是蘇先生的反射鏡Strehl Ratio低於0.9但接近 Strehl Ratio 0.8 。這可以轉移為表面精度約1 / 8波P.V.,符合室內的測試結果。

我們很少有機會進行A與B測試2塊相同口徑而有 Strehl Ratio 0.8和 Strehl Ratio 0.92的反射鏡。我們可以藉此機會得出以下結論: -
1 。 一塊1/8波P.V.和一塊1/17波P.V.鏡子都表現出色,並在大部分的時間很難分辨出其差異。
2 。然而, 1 / 17波P.V.鏡子將得出略高反差,但此差異只有在A 與 B的比較下才分得出。
3 。在一般清晰度的晚上,一塊1 / 17波P.V.的反射鏡往往比1 / 8波P.V.的反射鏡有更多機會看到較多細節。
4 。看來一塊具有較高Strehl Ratio的反射鏡在高倍率觀測月球表面時會給出更豐富的色調變化和更微妙的亮度。具有較低Strehl Ratio 的反射鏡往往會得出較為蒼白的月球影像。

蘇先生的反射鏡雖然不在1 / 20波P.V.超高精度範圍之內,他的反射鏡已經是非常好的作品而優於許多可以在市面上購得的。我很難想像會有任何人仕會不滿意其望遠鏡配備有一塊這麽好的反射鏡。

事實上我很欽佩蘇先生,所以我總是隨時願意向他聽取和學習,蘇先生無疑在自製天文望遠鏡人仕的圈子內是位于頂尖兒。

對不起,我已推遲等了很長時間提交本報告。再次抱歉我是用英文寫的,我不得不因為我弱(實際上,不知道如何)於在電腦上輸入中文。

最好的問候
陳玉麟
2008年九月14日。

苏鲁锭
主序星
文章: 280
註冊時間: 週六 19 8月, 2006 21:34

文章 苏鲁锭 » 週一 03 11月, 2008 23:45

谢谢TONGKW先生的翻译。谢谢!!
再次感谢陈先生的辛苦检测。
磨镜子真是磨到老也学不完。
在陈先生手上的镜子,当时的检测由于没有注意到镜面的第一次反光。影响了镜子中心的检测精度。
当时镜子还在我的手上。陈先生算出中心有凹陷,我就反复的细看。后来我用东西将镜子的中心遮挡了30MM就可以清楚的看到了这个小毛病了。为了保持镜子的真实性。我没有再修这个镜子。
现在再磨镜子的检测,就比给陈先生的镜子好多了。
最後由 苏鲁锭 於 週二 04 11月, 2008 00:01 編輯,總共編輯了 1 次。

苏鲁锭
主序星
文章: 280
註冊時間: 週六 19 8月, 2006 21:34

文章 苏鲁锭 » 週一 03 11月, 2008 23:57

陈先生用的这个方法以前我也用过3-5年。
由于它要反复计算。才能有结果。在磨制过程中是个麻烦的事。
还有就是发线在镜面的精确位置不易定的很准。影响计算的精度。
有个朋友送我一个软件。可以很快的计算。但是我试了,当镜面发线的位置的测量误差大于2MM时,计算的误差就有1/12波长。所以后来我就再也不钻研这个检测方法了。现在我就没有办法用这种方法检测镜子了。
但是我现在发现,我还是要钻研这个检测方法。因为将来磨500以上的大镜子。我是没有办法用平面镜来检测的。
有时间我将用我这次磨的300抛物面试一试这种检测方法。

頭像
Wah!!
夸克星
文章: 13264
註冊時間: 週一 15 3月, 2004 21:28
聯繫:

文章 Wah!! » 週三 05 11月, 2008 01:55

Surface accuracy 1/8 wave P.V. Sthrel ratio : 0.82.
Surface accuracy 1/17 wave P.V. Sthrel ratio : 0.92.
http://www.rfroyce.com/standards.htm

From the above website:
1/8 wavefront error should give Strehl Ratio 0.95
1/17 wavefront error should give Strehl Ratio > 0.978

Why the numbers are so different??? :roll: :roll: :? :?

Chanlunlun
夸克星
文章: 3791
註冊時間: 週四 09 10月, 2003 21:06

文章 Chanlunlun » 週三 05 11月, 2008 10:17

Wah!! 寫:
Surface accuracy 1/8 wave P.V. Sthrel ratio : 0.82.
Surface accuracy 1/17 wave P.V. Sthrel ratio : 0.92.
http://www.rfroyce.com/standards.htm

From the above website:
1/8 wavefront error should give Strehl Ratio 0.95
1/17 wavefront error should give Strehl Ratio > 0.978

Why the numbers are so different??? :roll: :roll: :? :?
Dear Mr. wah !!,

Mirror surface error and wavefront error are not the same thing.

Surface P.V. = 0.5 times wavefront P.V.

Therefore

1/8 wave wavefront P.V. = 1/16 wave mirror surface P.V.
1/17 wave wavefront P.V. = 1/34 wave mirror surface P.V.

Best regards
Chan Yuk Lun

頭像
Wah!!
夸克星
文章: 13264
註冊時間: 週一 15 3月, 2004 21:28
聯繫:

文章 Wah!! » 週三 05 11月, 2008 12:24

Do you mean Mr. Su's mirror is 1/4 wavefront PV, which is just meet Rayleigh limit lowest requirement?

回覆文章

回到「望遠鏡 廠制儀器 測試報告專欄 Telescope Testing Report Center」

誰在線上

正在瀏覽這個版面的使用者:沒有註冊會員 和 1 位訪客