The making of 30 in telescope - 34, OTA finished.

夸克星 註冊時間: 2003-10-09 文章: 2207

Dear ATMs,

The OTA has just been completed. As expected the whole equipment looks huge, after all it is a 30 inch telescope.

Unlike traditional Dobsonian, the mounting of the OTA to the alt-alz mount is a 3 point design. On the port side of the OTA is a 10 inch disc loading onto 2 teflon bearings while on the starboard side the loading of the telescope is taken up by a single 1/4 inch ball-bearing. The advantage of such design is that it will gives a smoother rotation of the telescope in the altitude axis, while giving sufficient friction to hold the OTA in place even small un-balance occurs.

At the moment the telescope is seen in its version 1.0 outlook. We will make further experiment on the telescope :-

1. A 8.5 inch optical flat will be grinded to replace the small 4 inch diagonal. After this modification we no longer need intruding focuser. The zenith eyepiece height will also be reduced by 5 inches.

2. A folded Newtonian will be constructed by the 8.5 inch optical flat. In this case the zenith eyepiece height will be reduced by 29 inches compared with the original, giving a very compact design. However focuser still intrudes into the light path .

3. A 5.5 inch Cassegain secondary will be grinded, giving a floded Cassegain design, with non-intruding focuser. The zenth eyepiece height is only a little more than 4 feet, giving a very compact design.

4. A 54 point flotation mirror cell will be constructed to see how it performs comparing with an 18 point cell.

Although in its un-modiofied version the telescope is now ready to be put into operation once the mirror is silvered.

Best regards
Chan Yuk Lun
5-2-2006

夸克星 註冊時間: 2004-12-13 文章: 6008 來自: NT

恭喜，恭喜。

夸克星 註冊時間: 2003-10-09 文章: 2207

XR250 寫到:

恭喜，恭喜。

Dear Mr. 250,

Thanks.

What you are seekng now is only the basic version of the telescope. We are going to add two motors for electric slow motion control and later, perhaps a GOTO system onto the telescope, making targeting more easily.

Best regards
Chan Yuk Lun

夸克星 註冊時間: 2004-12-13 文章: 6008 來自: NT

有無磅過成座鏡有幾輕？

夸克星 註冊時間: 2003-10-09 文章: 2207

XR250 寫到:

有無磅過成座鏡有幾輕？

Dear Mr. 250,

The mirror itself weighs about 40 lbs. The whole telescope, including the eyepiece and finderscope, weighs less than 80 lbs. If we add two electric driving motors and batteries, perhaps 1 to 2 lbs more to the total weight. Think about this : a C-8 together with equatorial mount and accessories can easily tally to 50 lbs.

The whole structure is made by thin plywood. That's why it weighs so little.

Best regards
Chan Yuk Lun

紅巨星 註冊時間: 2003-06-28 文章: 464

陳Sir

我發覺你製作的望遠鏡除了口徑大，精度高外，尚有幾個特點：

1)使用率高，由於輕便，搬運容易，自然使用次數多，比一般"大笨象"要一大班人搬運，用幾次後，就放在雜物房蒙塵。

2)使用方便，利用人體工程作基礎，考慮人體高度，視線。不需爬高俯低，可以舒適地享受夜空，而且避免在長梯頂險像橫生。

3)實用，每一個部份都以實用為出發點，鏡面精度不吹毛求疵，只求足夠便可，主鏡座浮動也是如此，整枝鏡無一點多餘地方。

4) 全自製，完全實現手工製作精神。

5)價格比最高，以最低價錢製作出最高質望遠鏡，完全打破市場"口徑價格定率"-- 口徑增加一倍，價格增加四倍。

所以兩位高手，Chan Sir 價廉物美，而Wong Sir 就追求完美，方向不同但各領風騷！！

ChanSir 自謙手工比不上WongSir，但他成立的"哈雷"是香港唯一自己生產望遠鏡的公司，不單主鏡，金屬部件，連電鍍也一手包辦，而產量有數百枝，不可謂不驚人，除此以外尚生產接環、微動雲台等，可想而知Chan Sir 金工方面的造藝甚高，只是他不輕易露一手，"鏡神"不是過譽，功力深不見底。

ChanSir成功磨製消色差折射鏡，而WongSir 就製作卡式，又各有特色

ck

夸克星 註冊時間: 2003-10-09 文章: 2207

CK 寫到:

陳Sir

我發覺你製作的望遠鏡除了口徑大，精度高外，尚有幾個特點：

1)使用率高，由於輕便，搬運容易，自然使用次數多，比一般"大笨象"要一大班人搬運，用幾次後，就放在雜物房蒙塵。

2)使用方便，利用人體工程作基礎，考慮人體高度，視線。不需爬高俯低，可以舒適地享受夜空，而且避免在長梯頂險像橫生。

3)實用，每一個部份都以實用為出發點，鏡面精度不吹毛求疵，只求足夠便可，主鏡座浮動也是如此，整枝鏡無一點多餘地方。

4) 全自製，完全實現手工製作精神。

5)價格比最高，以最低價錢製作出最高質望遠鏡，完全打破市場"口徑價格定率"-- 口徑增加一倍，價格增加四倍。

ck

Dear CK,

Thanks for your valuable comments. What you've said precisely describes my value in ATMing.

A telescope has to be cheap in fabrication otherwise it is better off to buy one.

A telescope has to be light weight otherwise you never use it seocnd time.

A telescope has to be convieient in use otherwise it damages our spine.

A telescope has to be big otherwise people will be disappointed looking through it ( too much computer enhanced photos on internet distording people's value )

Last but not least I insist on making oneself's own optics. After all we are making telescope. We are not making furniture.

Thanks again for your comments. Hopefully I will hear more about your opinion in future.

Best regards
Chan Yuk Lun

紅巨星 註冊時間: 2003-07-26 文章: 450 來自: Hong Kong

I wish I shall have a chance to see this 'big Dobs'!

夸克星 註冊時間: 2003-10-09 文章: 2207

starship 寫到:

I wish I shall have a chance to see this 'big Dobs'!

Dear Mr. Starship,

Of course you will. The telescope is ready now but we need to do some painting and minor modification jobs.

When we go star gazing we will announce in this forum. Stay tuned.

Best regards
Chan Yuk Lun

中子星 註冊時間: 2004-06-18 文章: 1119 來自: 香港

that's great...hope to have chance to join u guys^^

夸克星 註冊時間: 2004-11-08 文章: 8115 來自: 香港

陳sir,看不清中間那幾根支架是什麼材料做的
好幼哦,
另外控制鏡子左右移動的裝置在哪?

夸克星 註冊時間: 2003-10-09 文章: 2207

Tarepanda 寫到:

陳sir,看不清中間那幾根支架是什麼材料做的
好幼哦,
另外控制鏡子左右移動的裝置在哪?

Dear Mr. Panda,

The slim pole that you mentioned is the struss for connecting the secondary cage to the mirror box. The struss, although thin, keeps the optical alignment precisely no m,atter where the telescope points to.

There are four roller installed at the bottom of the alt-alz mount to serve as azimuth bearing. I'm sorry that they are no shown in the attached picture.

Best regards
Chan Yuk Lun