Available Instrument Setups
Following instrument setups are available:
Linear polarimetry imaging using calcite (not usefull for extended objects!)
Circular polarimetry imaging using calcite (not usefull for extended objects!)
Linear spectropolarimetry
Circular spectropolarimetry
Linear polarimetry imaging using polaroids (for extended objects)
NOTE:
It is not possible to change between half wave and quarter wave plate during an observing run, but it is possible to do both linear and circular polarimetry simultaneously using the quarter wave plate, at the cost of ~50% loss of efficiency in the linear polarisation.
Following slits are available for spectropolarimetry:
Pol_1.0" (actual width 0.7")
Pol_1.4" (actual width 1.2")
Pol_1.8" (actual width 1.5")
all 15" long
NOTE:
Only one slit can be mounted at a time as there are only two calcites available!
Orientation of the Calcites:
By default, the Calcite is mounted such that the ordinary and extraordinary beam are split up vertically ("Vertical Mount"). This has the advantage that the readout time for spectropolarimetry is reduced significantly compared to the "Horizontal Mount".
Readout times for typical spectropolarimetry windows are ~40s for the "Horizontal Mount" (vertical spectra) and ~13s for the "Vertical Mount" (horizontal spectra).
If requested by the observers, the Calcites can be mounted horizontally. Reasons to change the Calcite mount are:
The "Vertical Mount" has the disadvantage that dead columns will always end up at a certain wavelength. Observers that are especially interested in certain lines might be affected by this and might thus consider "Horizontal Mount".
For observers doing fast polarimetry, the "Horizontal Mount" is much more convinient as it will yield shorter exposure times.
NOTE:
Please inform staff well in advance if you want to use "Horizontal Mount".
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