24 inch telescope - sad news and how we overcome it

[Chanlunlun]

For the coating part, i have heard that using chloroform and some plastic can DIY a appreciable solution of coating layer which can protect the silver surface from the polluted air in HK.
But i have forgotten which kind of plastic it is.

Dear Mr./Miss/Mrs Simonii,

Thanks for your concern. However using chloroform to deposit a protective layer may not be uniform enough to secure the necessary optical perfection for an astronomical mirror.

I have searched the webn and it seems that there is no way to form a protective layer over silver by chemical or mechanical means.

Best regards
Chan Yuk Lun

[Chanlunlun]

Mirror God,

You are my hero.

Dear WongSir,

Please don't say this. If you can remember I had phoned you several times asking about your advices before we really carried out the silvering process.

So I must express, on behalf of Queen's College , our gratitude to you.

Best regards
Chan Yuk Lun

[扒飯撈麵]

4. Dextrose – buy it in all super market in cheap cheap price.

what is it???
sth containing -CHO ???
我還以為可以用葡萄糖tim

[01307699d]

dextrose係右旋葡萄糖呀，即係平時食得果隻囉
cloudy mud 係銀黎，咁這個plating咪好貴囉，嘥咁多silver nitrate
咁係唔係deposit 幾層銀呀，咁鍍這塊鏡咪好好好貴!!!

[01307699d]

我想問塊銀鏡一段時間要再鍍的原因係刮花或因為silver sulphide問題呀???

如果係silver sulphide問題就簡單d啦，因為我睇過有個網話，其實想將塊鏡同錫紙放係鹽水當中，等十分鐘左右就還原返啦，仲好閃添!!!

不過刮花就 ...............再鍍過啦

[Chanlunlun]

4. Dextrose – buy it in all super market in cheap cheap price.

what is it???
sth containing -CHO ???
我還以為可以用葡萄糖tim

Dear Mr. Noodle,

Dextrose is in fact D-Glucose. At a price of HK$16 you can buy enough for silvering hundreds of mirrors.

Best regards
Chan Yuk Lun

[Chanlunlun]

我想問塊銀鏡一段時間要再鍍的原因係刮花或因為silver sulphide問題呀???

如果係silver sulphide問題就簡單d啦，因為我睇過有個網話，其實想將塊鏡同錫紙放係鹽水當中，等十分鐘左右就還原返啦，仲好閃添!!!

不過刮花就 ...............再鍍過啦

Dear Mr/Miss 01307699d,

We re-coat the mirror solely because of contamination of silver by sulphide in atmosphere.

If what you are saying is true then we have already gained a piece of extremely valuable information. Using a silvered mirror will be more convenient than using an aluminized mirror.

Thanks again for your priceless advice.

Best regards
Chan Yuk Lun

[Chanlunlun]

cloudy mud 係銀黎，咁這個plating咪好貴囉，嘥咁多silver nitrate
咁係唔係deposit 幾層銀呀，咁鍍這塊鏡咪好好好貴!!!

Dear Mr/Miss 01307699d,

We have used 21 grams of silver nitrate for this coating process. So this is the cost - 21 grams of silver nitrate.

We don't know how much it cost, as we are supplied unlimited amount of silver nitrate by our school.

Best regards
Chan Yuk Lun

[Subaru]

It is essential to keep the silver layer as fresh as possible when telescope sees first light, at least we have the highest possible reflectivity.

Best regards
Chan Yuk Lun

絕對是. 我在中學時也試過把自己的5"吋鍍銀, 不過在屋企做, solution也不夠, 鍍得唔係好均暈, 記憶中鏡面唔夠一個月就開始濛.

[01307699d]

我查過啦，1磅silver nitrate 要us$250
咁我計過鍍塊鏡都大約要$80-90喎
不過學校既，就.....唔使啦

[Chanlunlun]

我查過啦，1磅silver nitrate 要us$250
咁我計過鍍塊鏡都大約要$80-90喎
不過學校既，就.....唔使啦

Dear Mr. 01307699d,

Thanks for checking me the price of silver nitrate. We have figured out that for the 24 inch mirror we need 90 grams of silver nitrate which means that the cost for coating of the big mirror is about HK$ 400.

It is much cheaper than sending the mirror to get an aluminizing job out of HK. The quotation for sending our 24 inch mirror to USA for an enhanced aluminium + overcoat tally to around HK$8,000. including the shipping by UPS.

Theorectically silver has a reflectivity of 98%, much higher than that of aluminium, still better than ehanced aluminium. Now it is even at such a lower price that it sounds very logical to switch to silvering instead of aluminizing the big mirror.

But theory is just theory.

Best regards
Chan Yuk Lun

[01307699d]

原來拎去美國要咁貴架，咁講$400平好多喎
不過要睇下塊鏡個情況先知抵唔抵啦

我好期待睇到這塊鍍銀的鏡同鍍鋁的鏡有咩分別呀!!!

[Wah!]

如果每一個月,因為氧化(硫化?)要再鍍一次,經過一兩年時間的成本就變得很貴喇...所以我估要想辨法使到佢唔氧化才是真正達到低成本的效果.

[Chanlunlun]

如果每一個月,因為氧化(硫化?)要再鍍一次,經過一兩年時間的成本就變得很貴喇...所以我估要想辨法使到佢唔氧化才是真正達到低成本的效果.

Dear Mr. Wah!,

Totally agree with your view. Before we really experiment the life-span of silver layer it is too early to estimate the cost of silvering.

Searching in the web we have discovered both positive and negative opinions about silvered mirror. While majority speculates that silver can at most last for a few weeks ( isn't that too short a life time ? ) before it tarnishes into useless some end users of silver mirrors ( mostly in Australia and New Zealands ) reported that their silvered mirror last for several years and one even claimes that the his silvered diagonal has been put under satisfactory service for 10 years, environmented by the air of urban district.

The only way to prove above statements, as far as I can imagine, is to try it out yourself. This is what we are doing now, though reluctantly.

Best regards
Chan Yuk Lun

[Zephix]

我打聽到樟木頭有間廠可以做24"電鍍既工作 (鍍銀/鋁)均可~
但價錢未知, 如有需要可幫你問問價~~~