(a) STELLA-I in the foreground with its AG-unit (black box) in the right Nasmyth focus (with the fiber cable making a loop). STELLA-II is in the background. (b) Accumulated guiding corrections for a 1-hour exposure with the SES on STELLA-I. The dots are the individual alt-az pointings. The circle indicates the fiber entrance diaphragm of 120 m (2.5 arcsec). The guiding rms was 0.19 arcsec in azimuth and 0.24 arcsec in altitude.
