report on 14 inches telescope - one

[Chanlunlun]

Dear sky gazers and ATMs,

After waiting patiently for 10 days we finally receive the coated 14 inches mirror from Zhitong on 25th August, 2003. The box opening process was full of excitement and "fun". While opening the box the first glance on the mirror was that it did not look like what we were expecting :- the reflectivity seems to be a little bit low and there is a pale red color about 8 inches diameter in the central region. The most terrible thing we fear about was that the mirror could not achieve the light grasp as we expected and handicapped its performance in deep sky observation. There is numerous test for this equipment and the light grasp test is certainly among one of them.

This telescope is built primarily for deep sky viewing in rural area. The total weight the telescope is about 50 lbs. including the equatorial platform. It can be taken out to MTR, bus, ferry and taxi easily (well, quite easily ) by one student if the equatorial platform is not included. If the equatorial platform is insisted to be carried along with, then 2 students will be more than sufficient. The factor of portability by one or no more than 2 person on public transportation vehicle is fully taken care of during the designing process.

The first object for star test of the 14 inch telescope is to see whether it could be taken out by one man easily on public vehicle. The telescope was taken out from my home on the nights of 29th August and 30st August to 「Water Mouth」 by public transport for deep sky viewing. On both occasions it had proved that the whole telescope, together with the equatorial platform, was capable of being transported by a single man with absolute no extra assistance. There was also no big difficulties encountered when jumping onto a taxi,, bus and MTR with above said equipment. The telescope undoubtedly passed the transportation test.

For those who would like to DIY their telescope I would like to share my experience :-

1. Think twice on how much you love the hobby of sky gazing before starting the project. If you are not really addicted to skygazing then do not start DIYing your telescope or otherwise you most probably end up with a long tube with a bulky mounting resting at some places in your living room or bedroom idling for years, not to mention the dirts and garbage you would create during the implementation of your project.
Sooner or later your parents/brother/sister/wife/husband/girlfriend/boyfriend will start complaining about your invasion into their territory. It is not uncommon that most telescope, especially for big ones, receives star light only once per several years or decades or worst, per whole life.

2. Think twice what targets your telescope is aimed at before you start your project. A telescope aimed for deep sky viewing should has as large an aperture as possible yet handy enough for transportation to remote sites for proper functioning. Furthermore a Dobsonian mount is almost a must for being easier for star hobbing than an equatorial mount. In addition it is extremely unrealistic ( and foolish ) trying to make an 「portable」 equatorial mount for big Newtonian. On the other hand if you are interested in planetary observation you most probably end up with a mid-size equipment with aperture no bigger than 10 inches supplemented by a heavy duty full function equatorial mount. Such equipment most probably lying in the roof of your house or in your backyard ( if you are so lucky to have a backyard ). If you are one of the majority who would like to use your telescope for low power wide field deep sky viewing while at the same time also require the same equipment for high power planetary observation ( and taking photos! ) you most probably end up with an equipment too heavy to be portable while at the same time too small to show fantastic deep sky views.

3. Except that you are only interested in imaging solar system objects the telescope you DIYing should be used in rural/suburban areas with rather dark sky, rather good transparency and stability. Hence your equipment should be designed as light weight as possible while at the same time it should be packed into as small a package as possible for easy transportation. There is an old saying that the best telescope is the one you use most. The telescope that cannot be moved by you must not be a good telescope.

4. Whether you are going to buy a finished mirror or grind the mirror by yourself, you should make as big an aperture as possible. It is rather likely that this is the only chance you make your own telescope during the whole life, so make the best use of the opportunity when it happens.

5. Never make a telescope with the eyepiece height taller than youself. Soon you will discover that bringing a ladder to observation site is no more easier than bringing the equipment themselves. While on top of a ladder you will find yourself jeopardize to danger of falling down, it just doesn』t worth it.

6. Whatever aperture you choose to make, make a Newtonian. Don』t try to make a Cassegrain, a refractor , a Maksotov or a Schmidt. Don』t even try to think about it. It happens that Newtonian performs best in terms of visual capability and simplicity. Additional bonus is that if you fail to make good optics, you are always able to buy commercial replacement in a very reasonable prize.

These are my experiences during many years of mirror pushing and laboring myself in taking telescopes into rural site for star gazing. Hopefully they would provide some insights to those who would like to DIY their equipment in recent or more distant future.

Best regards.

Chan Yuk Lun

[sodium]

好靚呀．．．．．．間屋
呢渡係chan sir屋企?
幾時比我上黎玩呀

[Wongsir]

陳玉驎兄,

看見你和學生一同自製的14吋杜蘇式望遠鏡,真個令我開心和佩服.

想當年,(sorry,我老了,所以常常想當年),
香港第一代磨鏡者(1970年代),關耀平,陳鑄略,鮑國全,潘德生和
我等等互相交流經驗和去學校推廣磨鏡,希望把自製望遠鏡的方法介紹開去,
令一些沒有能力購買昂貴儀器的天文愛好者,自己也擁有一枝天文望
遠鏡.
1980年代,你們這批新力軍接力研製各種類形的望遠鏡,若我無記錯,
應該就有你和梁鑑章,童偉輝,蔡坤安,譚志強等等.

不過玉驎兄能夠維持自已興趣近30年,卻真是難得.

而更難見得到的,就是你能夠把自己的知識無私的全部傳授下一代,
這種精神,真真要向你學習.

磨大口徑望遠鏡不單是技術,而毅力恆心和體力比起磨5吋小鏡
真是困難得多,旁人難以感受,當透過自製大鏡觀看深空天體,喜悅心情
卻難以筆墨形容.

讓我們繼續努力, 推廣磨鏡精神.

Wongsir
12-10-2003

[Subaru]

好靚呀．．．．．．間屋
呢渡係chan sir屋企?
幾時比我上黎玩呀

而且還好大tim!

陳前輩講嘅野真係好到point.

[alyf]

間屋既設計同支鏡一樣, 發揮出何為 "簡約主義"!

[CK]

陳玉驎兄,
自上次壁屋一別，屈指一算，己十多年沒有聯絡，想必別來無恙！見你的學生製作的14吋，可見你依然堅持由主鏡到主鏡座己至支架的DIY精神，佩服！！佩服！！睇完上面篇文章，就好希望可以見多一些這些實幹的硬料文章，而家討論區好少這些本地土產的技術文章，而Subaru兄的論鏡就是其中表表者，如果能加上你的做鏡技術文章，必牡丹綠葉，能使後進有心人，得一捷徑，踏入做鏡大門，希望你能抽空，多些上這裏發表心得。

我記得在二十多年前，曾拜讀你的一糸列文章，致今依然印像深刻。就是你於理工天文學會期刊中發表你的做鏡心得，該等資料參考價值什高，如果讓它們流失，湮沒實在可惜。WongSir 如果能成立一個文章精華區，將這些技術文章分門別類整理好，作為技術資料庫，我相信對做鏡者方便很大。

譚志強

[sodium]

佢仲話支鏡架係臨時架炸~
不過臨時都用到34十年~~

[Wongsir]

陳玉驎兄,
......

我記得在二十多年前，曾拜讀你的一糸列文章，致今依然印像深刻。就是你於理工天文學會期刊中發表你的做鏡心得，該等資料參考價值什高，如果讓它們流失，湮沒實在可惜。WongSir 如果能成立一個文章精華區，將這些技術文章分門別類整理好，作為技術資料庫，我相信對做鏡者方便很大。

譚志強

ck,

不知是巧合還是有緣,早幾天我整理一下舊磨鏡資料,準備增補
望遠鏡裝作機械部份文章,我竟發現了兩頁已呈黃色的F4紙印
的筆記,它就是陳玉驎20多年前利用蝸輪齒設計赤道儀的文章.
想當年我也有參考玉驎兄的方法去製作我的笫二枝望遠鏡,
就是那次得獎的牛卡式望遠鏡,算上去他的筆記也有功勞呢.

讓我問準玉驎兄後,我會把這份珍貴文件scan上來迷宮,供各位
會員欣賞.

Wongsir
13-10-2003

[Subaru]

你們這批新力軍接力研製各種類形的望遠鏡,若我無記錯,
應該就有你和梁鑑章,童偉輝,蔡坤安,譚志強等等.


Wongsir
12-10-2003

原來CK是新力軍!

[sodium]

你們這批新力軍接力研製各種類形的望遠鏡,若我無記錯,
應該就有你和梁鑑章,童偉輝,蔡坤安,譚志強等等.


Wongsir
12-10-2003

原來CK是新力軍!

gum我係新新新力軍la~

[aristo]

你們這批新力軍接力研製各種類形的望遠鏡,若我無記錯,
應該就有你和梁鑑章,童偉輝,蔡坤安,譚志強等等.


Wongsir
12-10-2003

原來CK是新力軍!

gum我係新新新力軍la~

gum我就重未進軍.

[Subaru]

講起關老闆, 就要提一提, 據晚輩瞭解, 他是本港光柵試鏡法的始祖, 而且他對器材製作及天文攝影有很深厚的經驗, 大家上他公司買鏡時記住偷嚇師呀! (他有秘技去避免kick手的磨低邊問題.)

[豆豸苗]

咦. 好想知呢個秘技喎~ 因為我時常磨低邊.