After eliminating bad condition of circumstance (effect of atmosphere and vibration for 40M long optical way )，the project group achieved pre-segmenting successfully on April 12。

     Co-focus image produced by three hexagonal submirrors with 1.1M in diagonal for spherical mirror(MB) can concentrate 80% encircled energy within circle with diameter of 0.42 arcseconds，which is less than 0.47 arcseconds (best than requirement of LAMOST)。Accuracy of co-focus is from 0.1 to 0.2 arcseconds，less than 0.25 arcseconds(best than requirement of LAMOST)。

primary mirror consists of 37 submirror(first group pre-segmented mirrors in shadow )	image before co-focus	image after co-focus