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Focal plane masks for FOCAS polarimetry
In order to avoid blending of the ordinary and extraordinary rays, the
standard masks for polarimetry have eight slits (or slots) of 10.0 mm = 20.6
arcsec length aligned at equal intervals of a 11.5 mm = 23.7 arcsec length
gap (see figures). The standard masks are made of poreless ceramics
(fluorine mica). The currently available masks are shown in the table.
Note: 0.8'' center slit mask is unavailable from S22A.
Mask name | Slit width | Offset | Notes |
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for spectropolarimetry |
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0".4 center specpol. | 0".4 |
center (0".0) | |
0".6 center specpol. | 0".6 | |
1".0 center specpol. | 1".0 |
|
2".0 center specpol. | 2".0 | |
0".4 offset specpol. | 0".4 |
offset (113".4) | (1) |
0".6 offset specpol. | 0".6 | (1) |
0".8 offset specpol. | 0".8 |
(1) |
1".0 offset specpol. | 1".0 |
(1) |
2".0 offset specpol. | 2".0 |
(1) |
for imaging polarimetry |
---|
Imaging pol. | | | |
(1) for longer wavelengths only (e.g., 300B+Y47)
Figure 1. Schematic representation of standard masks for spectropolarimetry
Figure 2. Schematic representation of standard masks for imaging polarimetry
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