SARG - Filters set
SARG filters are listed in the following Table. In the table is also indicated the different position on the correspondent filter holder. PS= Preslit Slide; FW= Filter Wheel; FF= Flat Field lamp.
| Pos. | Name | Recipe | Application |
| Neutral Filters | |||
| PS3 | ND 0.5 | NG4 | Flux Calib. |
| PS4 | ND 2.0 | NG9 (1.40) | Flux Calib. |
| PS5 | ND 3.0 | NG9 (2.83) | Flux Calib. |
| Stray light rejection and Order Sorting Filters | |||
| FW2 | FW2 | BG40 (1.0) | Stray light rejection |
| FW3 | FW3 | KG4 (2.0) | Stray light rejection |
| FW4 | FW4 | GG455 (2.0) | Order Sorting |
| FW5 | FW5 | OG570 (1.0) | Order Sorting |
| Light Balance Filters | |||
| FF1 | FF1 | UG5 (1.2) + NG9 (0.3) | Flats Balance |
| FF2 | FF2 | BG24 (1.0) + BG40 (1.5) + UG3 (1.0) | Flats Balance |
| FF3 | FF3 | BG26 (3.0) | Flats Balance |
All filters do not affect focus since they are in parallel beam. Image maximum shift on the slit when inserting a filter corresponds to about 0.3 arcsec for a thickness of 3mm. All filters are tilted by 3 degrees to avoid ghosts.
Neutral filters
The neutral density filters are placed in the Preslit slide (5 positions available). Normal operation of SARG is with Preslit Slide in position PS1. Filter dimensions are f 12.7 × 2 mm. Mechanical dimensions of cell is f 20 × 14 mm. Cell mounted in wheel at tilts of 3 degree.
Light rejection filters
The order sorting and background suppression filters, as well as custom interference filters, are placed in the Filter Wheel (12 positions reserved). Normal operation of SARG is with Filter Wheel in position FW1. Filter dimensions are f 12:7 × 2 mm.Mechanical dimensions of cell is f20 × 14 mm. Cell are mounted in the wheel at tilts of 3 degree.
Light balance filters
Each Flat Field calibration lamp is equipped with colored light balance filters in order to reduce range in intensity due to the poor output of the lamps in the UV. Each lamp, with its color filter, is intended to be used in a limited wavelength region with one particular cross disperser. The flat balance filters are mounted in front of the respective lamps.
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