8吋鏡 - 拋光/球面化時遇到的問題

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
cytangjoseph
星際雲
文章: 43
註冊時間: 週一 10 8月, 2009 15:59

8吋鏡 - 拋光/球面化時遇到的問題

文章 cytangjoseph » 週二 05 6月, 2018 02:09

焦內:
圖檔

焦點:
圖檔

焦外:
圖檔
發現中央有山, 及邊沿有低邊.

請問師兄師姊, 可以用甚麼方法修正?

Chanlunlun
夸克星
文章: 3825
註冊時間: 週四 09 10月, 2003 21:06

Re: 8吋鏡 - 拋光/球面化時遇到的問題

文章 Chanlunlun » 週二 05 6月, 2018 06:40

You have a huge amount of turned down edge, difficult to cure by pitch lap.

Best suggestion : go to #1200 fine grinding and do polishing again with hard pitch. What is the f/no. of your mirror ?

cytangjoseph
星際雲
文章: 43
註冊時間: 週一 10 8月, 2009 15:59

Re: 8吋鏡 - 拋光/球面化時遇到的問題

文章 cytangjoseph » 週二 05 6月, 2018 16:30

Hello Chanlunlun,

it is 8 inch, f/6

thanks for your tips!!

:D

cytangjoseph
星際雲
文章: 43
註冊時間: 週一 10 8月, 2009 15:59

Re: 8吋鏡 - 拋光/球面化時遇到的問題

文章 cytangjoseph » 週二 05 6月, 2018 16:34

So I think the turned down edge is top issue for me to tackle first.

Will be it like going back to #1200, and grind with 1/3 W stroke?

Chanlunlun
夸克星
文章: 3825
註冊時間: 週四 09 10月, 2003 21:06

Re: 8吋鏡 - 拋光/球面化時遇到的問題

文章 Chanlunlun » 週六 09 6月, 2018 07:37

Back to #1200, mirror on top using 1/3 center to center stroke.

cytangjoseph
星際雲
文章: 43
註冊時間: 週一 10 8月, 2009 15:59

Re: 8吋鏡 - 拋光/球面化時遇到的問題

文章 cytangjoseph » 週二 12 6月, 2018 13:17

Thanks Mirror god!!

Past few days, as a bit too busy [ or lazy ;) ]to go back to #1200 and making a new pitch lap, I spent a few more hours with the pitch lap I am now using:

some ways to try to improve the rolled edge:

1. more frequent cold press for good contact

2. hands placed in the center of the glass, and not on the edges.

3. Keep movemnts horizontal and slow. Push ( and pull) the glass with whole body weight ( back straight, bend your knees and ankles). As in Tai Chi

4. 1/3 COC. Alternate Mirror on Top, and Tool on Top

5. stop the polishing after 10 to 15 minutes, and take a break of 5 to 10 minutes, not to let the glass and pitch to warm up

焦內(inside focal poiint):

圖檔

圖檔

焦點 (focus):

圖檔


焦外 ( outside focal point):

圖檔

圖檔


So far the rolled edge is much reduced. Still some turned down edge.

Next I am going to tackle the remaining turned down edge, and the hill in the center

thanks!!

[edited for mixup of inside focal point and outside focal point pics]

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 3 位訪客