Polishing of 24 inch mirror COMPLETED

[Chanlunlun]

Dear ATMs,

The polishing was proceeding astonishingly fast. We started polishing on the day before and we have fully polished the mirror by today. A real quick job.

While we have spent more than 15 working hours in making the full size lap, the real polishing only last for 5 working hours, even with a 14 inch lap. We are also being particularly satisfied with the quality of the polished surface – there is not a single scratch or any pit hole on it. The surface is being perfectly smooth and transparent.

We have drawn our conclusion. The reasons for fast polishing may be due to the facts that

1. the polishing powder is a real fast stuff. Judging from its expensive price and the appearance, most probably it is premium grade Cerium Oxide specially for optical industries. Cerium Oxide polishes at a speed 5 times faster than Rouge.

2. The mirror had gone through a #2000 fine grinding instead of just #1200. In this way the mirror surface is finer than usual and saves a lot of polishing time.

3. last but not the least, we have our secret weapon – human fresh polishing machine. It is comprised of a team of young students who possess unlimited energy reserve. They just loved to push anything ( mirror, tool, lap ) on their hand hard and fast. That』s part of the reasons why we polished the mirror fast.

How about the profile of the surface ? Is it a dog biscuit? A hyperboloid ? An oblate sphere ? Turn down/up edge? A central hole?…………well, we have no idea. Because the polishing proceeded unexpectedly fast we have no time to build the tester and the mirror holder ( a real big one! ).

Anyway it doesn』t matter since we still need to remove a lot of glass to reach the f/3.5 paraboloid.

Our next step is to parabolize the mirror but before doing so we need to complete the Offner null tester first.

Best regards
Chan Yuk Lun
5-3-2004

[豆豸苗]

wow~ looks good ~~ ^^

[Wah!]

排牙好有型呀! 哈哈哈...
真係好快!!!!!!!!!!!

[Subaru]

快得好驚人!:shock: 睇嚟#2000沙真係有料到! 我以前用白色拋光粉, 覺得很慢.

點解有d啡色嘅? 乜Cerium Oxide唔係白色嘅咩?

以陳sir同班學生嘅進度, 睇嚟陳sir有機會可以提早開班教我地整超輕便杜蘇.

[天屍仔]

Chan Sir, should we find a better lens for null test??

[WenXP]

wow~ 恭喜!!! ^^