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Table 2
HERMES main parameters.
| Spectral resolution | |
| HRF | 85 000 (with slicer) |
| LRF | 63 000 (interlaced with simultaneous |
| Thorium spectrum) | |
| Fibre aperture | |
| HRF | 2.5 arcsec (80-μm fibre) |
| LRF | 2.15 arcsec (60-μm fibre) |
| Sampling | |
| HRF | 2–2.7 pixels |
| LRF | 3.1–3.8 pixels |
| Spectral range | 377–900 nm (in 55 orders) |
| Spectrograph layout | White-pupil layout on 1.2 × 2.4 m bench |
| Beam diameter | 152 mm |
| Collimator focal length | 1400 mm (f/9.2) |
| Echelle grating | θ = 69.74°, 52.676 gr/mm, 154 × 408 mm |
| Cross disperser | 2 PBL1Y prisms, 37.4° apex angle |
| Camera focal length | 475 mm (f/3.1, 6 lenses) |
| Detector | 2048 × 4608 13.5-μm pixels, thinned BI |
| CCD with graded AR coating | |
| Peak efficiency | |
| HRF | B: 21%, V: 28%, R: 25%, I: 17% |
| LRF | B: 15%, V: 20%, R: 18%, I: 12% |
| Limiting magnitudes | 1 h exposure |
| S/NV = 20 | mV = 13.4 (HRF), mV = 13.2 (LRF) |
| S/NV = 100 | mV = 10.4 (HRF), mV = 10.0 (LRF) |
| Radial velocity error | ~2.5 m s-1 (short term) |
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