Metrology system, and apparatus including primary mirror

A metrology system for measuring an amount of displacement of a structure of apparatus including primary mirror, the apparatus including primary mirror including a primary mirror portion including a primary mirror and a primary mirror supporting portion to support the primary mirror, an elevation axis structural body to support the primary mirror portion, and being rotatable around an elevation axis that allows an elevation angle in an orientation direction in which the primary mirror is oriented to be changed, an azimuth mount to support the elevation axis structural body rotatably around the elevation axis, and being rotatable around an azimuth axis that allows an azimuth angle in the orientation direction to be changed, and a pedestal portion to support the azimuth mount rotatably around the azimuth axis, the metrology system comprising:

• an elevation axis base portion provided along the elevation axis, passing through a position where the elevation axis and the azimuth axis intersect, and being fixed to the azimuth mount;
• and
• an inclinometer disposed at a position of the elevation axis base portion through which the azimuth axis passes, and to measure an inclination angle of the elevation axis base portion.