10 hrs of rough grinding of 24 in mirror

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
回覆文章
Chanlunlun
夸克星
文章: 3847
註冊時間: 週四 09 10月, 2003 21:06

10 hrs of rough grinding of 24 in mirror

文章 Chanlunlun » 週日 08 2月, 2004 22:52

Dear ATMs,

Today we carry out another 4 hours of rough grinding on the 24 inch mirror. Upon finishing the schedule today we got a sagitta of 5.9 mm which means that we has reached a f/6.3 curve. About 50 cubic inch of glass has been successfully removed in this three days. We are half way from the ultimate f/3.5 goal.

But there is a minor problem – the little astronomical equipment store room has been turned into a mess by us. No wonder mirror grinding is a messy business.

Best regards

Chan Yuk Lun
8-2-2004
附加檔案
mess.jpg
After 10 hrs of rough grinding, the store room had been turned into a mess. The teachers will not be happy in seeing this.
mess.jpg (47.28 KiB) 已瀏覽 10395 次

頭像
Wah!
夸克星
文章: 9073
註冊時間: 週六 28 6月, 2003 01:19
聯繫:

文章 Wah! » 週日 08 2月, 2004 23:21

工具板邊剩幾厚呀?

Chanlunlun
夸克星
文章: 3847
註冊時間: 週四 09 10月, 2003 21:06

文章 Chanlunlun » 週一 09 2月, 2004 08:24

Wah! 寫:工具板邊剩幾厚呀?
Dear Mr. Wah!,

Thank you for asking.

About 20 mm thickness still remains. The tool will survive until #3000 fine grinding, don't worry.

Best regards,

Chan Yuk Lun
9-2-2004

bandofbrother
主序星
文章: 183
註冊時間: 週四 25 12月, 2003 19:38

文章 bandofbrother » 週一 09 2月, 2004 19:30

點解個張磨鏡台好似唔係好堅固,我屋企都有張類似既台,不過好搖下ge bor,你點樣防止張台搖??

Chanlunlun
夸克星
文章: 3847
註冊時間: 週四 09 10月, 2003 21:06

文章 Chanlunlun » 週一 09 2月, 2004 22:40

bandofbrother 寫:點解個張磨鏡台好似唔係好堅固,我屋企都有張類似既台,不過好搖下ge bor,你點樣防止張台搖??
Dear Mr. BandofBrother,

You are correct. The table is very shaky while we were grinding the mirror ontop. We use this table because we have no other choice, it is being the cheapest available on market.

There is a lot of misundrestanding about mirror grinding. One of them is that we must have a very robust table for doing the job. The ideal mirror grinding table should consists of a concrete cylindrical base with weight of 50 kg embedding a 6 inch ( at least ) diameter steel pipe up to waist level. Ontop of the pipe there should be a welded steel framework with a 1 inch plywood ( of course it must be circular in shape, with unkonown practical reason, but very good psychological effect ) with diameter 30% more than that of the mirror under work.

While such table is perfect for the work under consideration, a cheap folding dinning table can also fulfill the requirement. Although it oscillate and shaking quite an extend during the grinding, nevertheless it provides a very good support for the 24 inch tool and mirror. That's all we required.

Another advantage of the foldingtable is that it can serve as a dinning table, a table for reading, a table for a cup of tea........etc after we finish the mirror.

So, a folding table might be one of the greatest invention during the last century.

Best regards

Chan Yuk Lun
9-2-2004

Chanlunlun
夸克星
文章: 3847
註冊時間: 週四 09 10月, 2003 21:06

文章 Chanlunlun » 週一 09 2月, 2004 22:47

bandofbrother 寫:點解個張磨鏡台好似唔係好堅固,我屋企都有張類似既台,不過好搖下ge bor,你點樣防止張台搖??
Dear BandofBrother,

Sorry, it seems that I have not answered your question. How can we stop the poor folding table from shaking during work ? As a matter of fact, we don't and we can't. We just let it shake and vibrate as much as it wish.

It won't hurt anyway.

Bestg regards

Chan Yuk Lun
9-2-2004

頭像
Wah!
夸克星
文章: 9073
註冊時間: 週六 28 6月, 2003 01:19
聯繫:

文章 Wah! » 週一 09 2月, 2004 22:52

估計要用幾多磅40號砂至完成粗磨呢?

Chanlunlun
夸克星
文章: 3847
註冊時間: 週四 09 10月, 2003 21:06

文章 Chanlunlun » 週一 09 2月, 2004 22:56

Wah! 寫:估計要用幾多磅40號砂至完成粗磨呢?
Dear Mr. Wah!,

If my calculation is correct, we need a total of 26 lbs of #40 carbo and 19 hrs of work to finish the f/3.5 curve for 24 inch mirror.


Best regards

Chan Yuk Lun
9-2-2004

頭像
Wah!
夸克星
文章: 9073
註冊時間: 週六 28 6月, 2003 01:19
聯繫:

文章 Wah! » 週二 10 2月, 2004 10:06

嘩!買砂都用唔少錢呀!!!

Chanlunlun
夸克星
文章: 3847
註冊時間: 週四 09 10月, 2003 21:06

文章 Chanlunlun » 週二 10 2月, 2004 14:54

Wah! 寫:嘩!買砂都用唔少錢呀!!!
Dear Mr. Wah!,

26 lbs of #40 carbo costs HK$520. Fortunately we don't need that much in fine grinding. Hence we guess that we may pay a total of $1000 for purchasing the carbo and polishing agent.

The total budget alloted to build the telescope is $4500. Hopefully we don't make it over-budget.

Best regards

Chan Yuk Lun
10-2-2004

回覆文章

回到「自製天文望遠鏡 Amateur Telescope Making 」

誰在線上

正在瀏覽這個版面的使用者:沒有註冊會員 和 9 位訪客