The M1 blank has been manufactured by the german company SCHOTT AG. It is made of ZERODUR, a glass ceramic with nearly null thermal expansion, commonly used for telescope mirrors and other engineering projects which require of using high accuracy not deformable surfaces. It weights 2366 kg and has an outer diameter of 2640 mm.

The blank for the JST250 M1 has been manufactured by the german company SCHOTT AG and accepted by AMOS, the company in charge of the manufacturing of the JST250 telescope. The blank has been shipped to AMOS headquarters in Belgium to proceed with the fine, final polishing.

The blank is made of ZERODUR, a glass ceramic with nearly null thermal expansion, commonly used for telescope mirrors and other engineering projects which require of using high accuracy not deformable surfaces. For instance, the 36 segments of Grantecan, the largest optical telescope in the world, are made of the same material.

The attached picture was taken during the JST250 M1 acceptance at Schott headquarters, together with Schott and AMOS staff. The blank weights 2366 kg, has an outer diameter of 2640 mm and a thickness of 250 mm. The inner hole, necessary for the light beam reaching the Cassegrain focus after being reflected in the secondary mirror, has a diameter of nearly 1010 mm.