DIY Focusing Masks

[willis]

There are several factors affect the image quality. With a modest scope and mount, if focusing comes to second, I don’t know what would be the first. Even without an accurate electric Feather Touch focuser, if you have a focusing mask, the focusing would be improved a lot. Of course, if you have both, the accuracy can be down to a few microns. The focusing mask can be bought from http://focus-mask.com/index.html. However, there is free template provided by this website. One can use cardboard to make their free lunch box. If you want a decent one, you can order one from the website. In fact I ordered two focusing masks last year. As I found it very useful and I got more telescopes now, I tried to DIY focusing masks of different size by myself. I used Smart Sketch to re-draw the focusing mask and then use laser cutter to cut it. I deliberate drilled different holes around the edge of the mask. This can help to fit different tube sizes. With the Smart Sketch I just need to draw one mask, refractor version, and the other size can just be done by scale the image. Here are my products:
60-66mm & 72-80mm focusing masks

有幾個因素會影響圖像質量。有了一般級數的望遠鏡和赤道儀，如果對焦因素排第二，我不知道哪個是第一了。即使沒有一個準確的電動羽毛調焦器，如果你有對焦遮罩將改善了很多。當然，如果你有電動羽毛調焦器和對焦遮罩，精度可到幾微米。對焦遮罩可在http://focus-mask.com/index.html購買。然而，這個網站有免費的模板提供。人們可以用硬紙板，自製免費午餐。如果你想有一個像樣的，你可以從網站訂購一個。事實上，我去年訂購了兩個對焦遮罩。當我發現它非常有用，現在我有更多的望遠鏡，我就自製了不同大小的對焦遮罩。我用Smart Sketch描繪畫對焦遮罩，然後使用激光切割機進行切割。我故意在周圍多鑽幾個洞，這可以幫助在不同大小的鏡筒使用。在Smart Sketch我只需要繪製一個面具(折射版本) ，其他大小可以簡單的放大縮小便成。這裡是我的成品：
60-66mm ＆ 72 – 80mm對焦遮罩

[社長]

Willis, can't agree more

一張照片的成像，是每個因素相乘的結果，是扣分制的，

望遠鏡光學成像 x 調焦 x 追蹤 x 視寧度.....

所以我一直說，太多拍深空行星月面的同好，太輕視調焦的重要性了。

你的魚骨板造得很好，謝謝分享

[willis]

社長,
u have both focusing mask & electric feather touch focuser. What accuracy can u achieve?
Willis

[社長]

Willis,
以魚骨版及電子調焦，可以把焦點調至最精確的一格，例如Feather Touch 3545調焦筒，配合電子調焦，每一格的變化是7.2um，所以我能做到焦準是+/-3.6um。而這情況下，Live View是幫不上忙的，我通常的做法是以人眼粗調後，再+/-5格每格拍一張，從11張中挑最好的，只要視寧度配合，一格已可看出變化。
這次在台灣高山上的溫差比香港大，由入夜至清晨失溫已超過四度，所以嚴謹的話，我的Kruppax鏡筒已已要重新調焦了。

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