APM 折射鏡筒物料 - Kruppax

Equipment (Telescopes) - 折射、反射、折反射,各類天文望遠鏡的技術訊息

APM 折射鏡筒物料 - Kruppax

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社長 » 2012-03-09, 01:14

過去數年在我的大力推動下,區內多了一大批APM折射鏡的用戶,從80到304APO不等,甚至現正動工的一台304APO雙筒鏡,這鏡的理論解像力達700APO,目視集光力接近500APO。受全球天文愛好者所推崇,四大登峰造極的折射鏡品牌:APM、高橋、TEC、Astro-physics,APM可說是處於領先地位,相比TEC、Astrophysics目前只造130至180APO、高橋大多集中在150以下,200以上絶少生產,年前才首次接單的300,APM單二月份已接單生產4台304APO。而現時全球最大的APO為APM 356APO,很快會被自己的510 f12.5APO取代,最快今夏於意大利中部落戶。

而各用戶對APM折射鏡最不瞭解的,可說是其鏡筒材料 Kruppax。一些愛好者對這方面沒深入研究,甚至嘗試買APM鏡頭回來,配上自製鋁筒或碳纖鏡筒,集中注意力在外觀上,以為比德國傳統製鏡工藝優秀。

我希望引述一段APM Markus Ludes的文字,去說明這種鏡筒材質的特性。實際上我2010年到訪意大利和著名光學設計大師Dr Massimo Riccardi見面時,他也提到相關訊息:

viewtopic.php?f=13&t=92

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The link to the tube material manufacturer
http://www.krueger-und-sohn.de/english/ ... .cfm?id=78

Protostar in USA use same material for tubes he sells worldwide for telescope makers
http://www.fpi-protostar.com/blite.htm
http://www.fpi-protostar.com/img/blite01.jpg

Over three times the strength-to-weight of plain cardboard tubes
Up to 40% lighter than cardboard or aluminum tubes
Moisture resistant
Excellent thermal properties

such tubes used for building telescopes since about 40 years by the famous belgium company “ Lichtenknecker Optics”. APM/TMB use it since the start in 1999. Many customers in USA and europe use it to build all kind of scopes.

The big advantage for LZOS Lenses: somehow this material cooperates better with LZOS Apo lenses then alu tubes and focuse shift due temperature change is smaller then with alu tubes, it means , customers has to do less refocusing during long time exporsures , prooved by many imagers and reported to me as here personal result.

Going out observing with the telescope from warm inside to cold winter night, optics getting a thermal shock and pinhsching heavily . Alu which cools down super fast supports such pinshcing, in some cases it can be critical and damage the glas, Krüpax 50 , a isolator material cools less fast down, so optics getting smaller cool down shock and less pinsching. This factor is important for customers living in very cold areas like north europe, canada, north china

Krüpax does not get as cold for fingers then alu , for some people who transport the scope in cold winter nights , nice to have here fingers not froozen to the tube

fast cool down alu tubes support fast dewing up of the optics, the apm design with Krüpax tubes and front dew shield baffle almost never dew up , here the Krüpax and front baffle works and acts a bit like a dew shield heater

alu tubes are available only in small diffrent diameter with thick wall, > heavy tubes > very difficult to mashine them thin, alu tubes could bend during such maschine down wall thickness and become unround , thats the reason Astro-Physics use such thick tubes and use the wall thickness to maschine baffles inside , the trade off he still have a thick tube and many alu material to cool down, will not much faster then Krüpax.

Only if you go the way as Matthias is doing, buiying large alu plates , roll them and welt them, you can get alu tubes with thinn walls and light weight ( like Vixen did on the smaller versions )

if you drop a alu tube to a corner, it can get a dent , Krüpax tubes cannot get dents , because they eat such shocks.

Krüpax has for us manufacturers also the advantage, we can get it fast, we can get it in any dimater we wish, in any wall thickness we wish and in any length we wish

the only 1 advantage alu tubes have : if they are mashined with thin tube walls they cool down faster, but this can be bad in nights of big huminity due fast dew up of the front lenses.

best wishes
Markus
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附上三張照片作參考:

- 228APO,以及多台254, 203等的物鏡組安裝方法,若用APM Kruppax CNC鏡筒,只需用附上的三顆M10縲絲緊貼固定在鏡筒端的法蘭上便可,不用Push-pull方法調光軸。當年第一次引進這口徑的APO時,聽到APM這樣的指引我有點擔心,因為就算三十年一台Royal Astro 76普消也有Push-pull結構的,心想APM是否太兒戲了.... 後來在香港及區內不同天文台架起這些大鏡後做的星空測試,也包括以數十米外設立人工星點測試,都一一顯示完美星像,最後我也信服了。

- 2010年冬,我的203APO把物鏡組拆去,鏡筒準備寄往台灣參加星空派對,物鏡組手提上機帶過去免受震盪,回來香港後又再裝上照常觀測。
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