请高手分析镜面光栅图

[美丽的星空]

大家新年好，近日抛光主镜出现下面的光栅图，麻烦高手分析以下镜面的面型，应该怎么纠正呢，254/1100，向内弯曲为焦点内。

[Water]

美麗的星空 兄：

從以上光栅測試照片顯示反射鏡可能出現 "磨低邊" 現象。閣下可參考壇主黃Sir於2006年12月的 "光柵測試鏡面法" 貼文內容，希望能幫助閣下解決磨製反射鏡方面的疑難：
http://www.hkastroforum.net/viewtopic.php?t=8235

[Chanlunlun]

Assume that the first picture is inside the center of curvature and the last is beyond.

Obviously you have a quite serious turned down edge. It is very difficult to cure by pitch lap alone.

The best solution is to go back to #1200 fine grinding for two hours ( or more ) and then polish the mirror again. The cause for turn down edge is too much force applied during polishing. Try not to press the mirror during polishing, it helps a lot.

[美丽的星空]

感謝二位分析結果，主鏡已經返細磨。陳先生，我發現在細磨最後階段邊緣1/5的區域總是比中間部分更透光，手法是1/4正心，不知是不是這樣導致的低邊？

[Chanlunlun]

If the edge is being semi-transparent after #1200 fine grinding - it means that the turn down edge is so serious that #1200 cannot undo it.

In this case you need to go back to #600 fine grinding until the whole mirror surface gets an even grayness.

[Water]

美麗的星空 兄：

修正磨低邊現象可參考壇主黃Sir於2012年7月16日的貼文內容，希望能幫助閣下解決磨鏡方面的疑難：
http://hkastroforum.net/viewtopic.php?p=248355

[美丽的星空]

感謝二位分析，重返細磨完成已經拋光4個小時，中心比邊緣要光些，光柵試鏡，邊緣1吋看不到反光，中心是標準球面