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Table 1.

Optical components of the VLT and SPHERE CPI visual path.

Abbr. Name r i e p Comment
VLT telescope
M1,M2 Telescope mirrors r alt.-az. orientation
M3 Telescope mirror r Strong pol. effects
CPI common path
Calibration sources i e Point and flat field sources, hole grid
HWP1 Half-wave plate 1 r i p Rotates M3 pol.
PTTM Pupil tip-tilt mirror AO, compensates M3 polarization
pol. calibration components i e p pol. characterization
HWP2 Half-wave plate 2 r i p Polarization control and switch
DROT Image derotator r Rotates image, strong pol. effects
TTM Tip tilt mirror AO
DM Deformable mirror AO
vi.BS Beam splitter Visual-infrared
CPI visual common path
ADC Atmospheric dispersion corrector r For visual
zw.BS ZIMPOL-WFS beam splitter e Gray or dichroic BS
Wave front sensor (WFS) arm
WTTP WFS tip-tilt plate Source positioning
SpF WFS spatial filter e AO tuning
WFS WFS-detector AO tuning
CPI visual coronagraph
Focal plane masks e Exchange wheel
Pupil masks e Exchange wheel

Notes. This incomplete list gives all important components for visual science observations. “Short” are abbreviations as used in this paper and Cols. 3–7 indicate whether the components are rotating (r), insertable (i), exchangeable (e), or/and only inserted for visual polarimetry (p)

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