Coating and installation of UT1 mirror M3

The tertiary, elliptical and flat mirror (M3) for the UT1 has been coated and is now being installed in its cell. Measurements show excellent reflectivity (91 %) and very little scatter roughness (8 Å). This mirror is placed on top of the M3 Tower that protrudes from the central hole in the primary mirror (M1). It directs the light from the secondary mirror (M2) towards the instruments at the Nasmyth platforms. (Photo obtained on July 30, 1998).