  GMagAO-X is the near first light ExAO coronagraphic instrument for the 25.4m
GMT. It is designed for a slot on the folded port of the GMT. To meet the
strict ExAO fitting and servo error requirement (<90nm rms WFE), GMagAO-X must
have 21,000 actuator DM capable of >2KHz correction speeds. To minimize
wavefront/segment piston error GMagAO-X has an interferometric beam combiner on
a vibration isolated table, as part of this "21,000 actuator parallel DM".
Piston errors are sensed by a Holographic Dispersed Fringe Sensor (HDFS). In
addition to a coronagraph, it has a post-coronagraphic Lyot Low Order WFS
(LLOWFS) to sense non-common path (NCP) errors. The LLOWFS drives a non-common
path DM (NCP DM) to correct those NCP errors. GMagAO-X obtains high-contrast
science and wavefront sensing in the visible and/or the NIR. Here we present
our successful externally reviewed (Sept. 2021) CoDR optical-mechanical design
that satisfies GMagAO-X's top-level science requirements and is compliant with
the GMT instrument requirements and only requires COTS parts.
