The making of 26 inch Cassegrain - 23, Semi-first Light

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
Chanlunlun
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The making of 26 inch Cassegrain - 23, Semi-first Light

文章 Chanlunlun » 週六 26 9月, 2015 11:20

Dear ATMers,

Although still in its raw state, the 26 inch Cassegrain managed to carry out its semi-first light on Friday, to celebrate to oncoming Mid Autumn Festival.

We chose this night for good reasons - first of all it’s a Friday night and student didn't need to go school next morning. Furthermore the primary mirror is still not yet silvered giving it the right amount of reflectivity to give the moon a very comfortable luminance, not to hurt students' eyes. Last but not least it gave a very good chance to test the whole operation of the telescope to see if there were any flaws. Actually there are flaws.

1. The telescope is too heavy to be pushed by hand. Such a big inertia is too difficult to be handled with by mere human flesh. ServoCAT + Argo Navis will be added very soon.

2. The cover for primary mirror is stupid. It could be be taken out from themirror box once the telescope is assembled. It has to be redesigned.

3. The diagonal cage is too heavy. We have to remake it to reduce the weight to ease the assembling and disassembling job.

4. The secondary mirror has a diameter of 10 inches (!!!). The secondary shadow inside the eyepiece view is noticeable even at power of 160X. This has no cure, unfortunately.

5. Painting of the whole structure has to be done ASAP otherwise humidity will eat up the wooden structure soon.


Despite all these shortcomings we were especially pleased with the Nasmyth focus of the telescope. It served what it is intended to - the eyepiece is always at the right height so that everyone can look through with ease, no matter where the telescope points to.

Oh one thing I nearly forget to tell - how it was like to view the moon with the biggest telescope in Hong Kong ? Well it's very solidly 3-D and the lunar surface is so full of details. The view is crisp.

The students were shocked by the detailed view of the lunar surface and also, by the sheer size of the scope. Once again astronomy was promoted among youngsters.

Best regards
Chan Yuk Lun
26 September 2015.
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102.jpg
Observing in the Nasmyth focus of telescope - a comfortable height.
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100.jpg
Semi-first light of the 26 incher.
100.jpg (324.23 KiB) 已瀏覽 5800 次
最後由 Chanlunlun 於 週日 27 9月, 2015 00:15 編輯,總共編輯了 3 次。

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bingsze
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文章 bingsze » 週六 26 9月, 2015 11:59

Well done. It's nice to be a queens student.

LT
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文章 LT » 週六 26 9月, 2015 17:28

擦新香港記錄。

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Eddy So
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文章 Eddy So » 週六 26 9月, 2015 22:59

LT 寫:擦新香港記錄。
X2

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wtyu21
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文章 wtyu21 » 週日 27 9月, 2015 06:09

Once if it “to show up” in PTC someday ~WOW! :shock: :shock: :shock:

Water
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文章 Water » 週日 27 9月, 2015 11:48

----
QUOTE

Johnny Sir 寫到:
Once if it “to show up” in PTC someday ~WOW!

UNQUOTE
----

Johnny Sir,鏡神大哥提及因望遠鏡的體積太大無法離開皇仁書院天台,相信閣下的願望落空了 ...

----
QUOTE

lawrencemok Sir 問到:
With scope that big,I guess it has to stay in school?Can't wait to visit it in coming open day.


鏡神大哥回覆:
Yes you are telling the truth. It won't leave the roof of QC. Come at open day and see.

UNQUOTE
----

引言貼文來源:
http://www.hkastroforum.net/viewtopic.p ... Chanlunlun

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Carl Chan
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文章 Carl Chan » 週日 27 9月, 2015 14:45

那個個副鏡比我的主鏡還大! [Good Job]

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Subaru
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文章 Subaru » 週日 27 9月, 2015 16:35

Congratulations!

Last time I watched over the lunar surface with a 0.5m reflector was severely deteriorated by seeing. This is encouraging with the performance Mirror God shared with this new Cassegrain.

Water
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文章 Water » 週一 28 9月, 2015 03:10

由2006年製成30吋牛反到今天2015年製成26吋卡式望遠鏡,小弟想問鏡神大哥閣下將來有沒有計劃製作更大型反射式望遠鏡? [疑惑]

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Steve
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文章 Steve » 週二 29 9月, 2015 11:04

[Good Job] [Good Job] [Good Job] [完美計劃]

其實大過廿四吋都幾難運送到夠黑的地方用。

Chanlunlun
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文章 Chanlunlun » 週二 29 9月, 2015 15:44

Water 寫:由2006年製成30吋牛反到今天2015年製成26吋卡式望遠鏡,小弟想問鏡神大哥閣下將來有沒有計劃製作更大型反射式望遠鏡? [疑惑]
I am always dreaming to remake the 30 inch telescope somewhere in future but the engineering challenge is too formidable.

Chanlunlun
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文章 Chanlunlun » 週二 29 9月, 2015 15:51

Steve 寫:[Good Job] [Good Job] [Good Job] [完美計劃]

其實大過廿四吋都幾難運送到夠黑的地方用。
We used to travel along with a 30 incher. The 30 inch telescope was actually once transported to Cheung Chau but weather was cloudy that night.

During the second star trip to Water Mouth the 30 inch primary mirror was broken into pieces by a careless student. We had very clear night that night together with a broken telescope.

Actually the 30 inch telescope, if it still survives, could be brought to PTC without very big problem, given that sufficient manpower is provided.

How was it like to view through a 30 incher ? I have no idea because the the mirror got no chance to collect photons from stars.

Water
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文章 Water » 週二 29 9月, 2015 16:12

----
QUOTE

鏡神大哥寫到:

During the second star trip to Water Mouth the 30 inch primary mirror was broken into pieces by a careless student. We had very clear night that night together with a broken telescope.

UNQUOTE
----

男人最痛是這種 ...

[遠目] [遠目] [遠目] [遠目] [遠目]

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Steve
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文章 Steve » 週二 29 9月, 2015 19:54

It is time, for the 30 incher, to reborn.

Chanlunlun
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文章 Chanlunlun » 週三 30 9月, 2015 11:03

Steve 寫:It is time, for the 30 incher, to reborn.
Technically very difficult lar !!

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