Observing Modes

PEPSI has of 2 permanently mounted fiber-fed focal stations (SX PFU and DX PFU). These units are used for target acquisition, guiding and wavefront sensing and house the mode selectors for utilizing the different PEPSI spectral resolutions as well as fiber coupling down to the spectrograph. Observations with the PFU can be done using 3 different resolutions: 100 µm fiber with R 250,000, the 200 µm fiber with R 130,000, and 300 µm fiber with R 50,000.

The SX and DX polarimeters are not permanently mounted. When mounted, they are at the direct Gregorian mount in place of the MODS instruments. The two polarimeters provide a full Stokes IQUV vector at a resolution of R=130,000

The entire spectral range from 381.9 to 906.4 nm can not be covered in a single exposure but rather with 3. PEPSI has two arms (independent of the SX or DX). The blue arm covers the spectral range from 381.9-542.5 nm with the cross dispersers CD1, CD2, CD3. The red arm covers the range from 536.1-906.4 with the cross dispersers CD4, CD5, CD6. The red and blue arms can be observed simultaneously with the exception of CD3 and CD4.