Table 3
Calculated parameters for seven dual FPI systems.
| Parameter/FPI system | CRISP | CRISPm | CRISP2 | CHROMIS | EST-B | EST-V | EST-R |
|---|---|---|---|---|---|---|---|
| Total length of FPI system (m) | 1.437 | 1.316 | 1.824 | 1.579 | 4.4-4.7 | 4.5-4.7 | 4.3-4.5 |
| Etalon clear aperture (mm) | (75) | (75) | (98) | (75) | 135 | 180 | 180 |
| FOV diameter (arc min) | 1.5 | 1.5 | 2.4 | 2.0 | (1.0) | (1.0) | (1.0) |
| Focal ratio at etalons | 165 | 165 | 140 | 120 | 110 | 147 | 147 |
| Output focal ratio | 55 | 23 | 20 | 31 | 25-60 | 25-46 | 19-35 |
| Cavity ratio d2/d1 | 0.381 | 0.381 | 0.381 | 0.381 | 0.381 | 0.381 | 0.381 |
| FP1 cavity gap d1 (mm) | 0.787 | 0.787 | 0.787 | 0.358 | 0.377 | 0.787 | 0.787 |
| FP2 cavity gap d2 (mm) | 0.300 | 0.300 | 0.300 | 0.137 | 0.144 | 0.300 | 0.300 |
| FP1 Reflectivity (%) | 94* | 94* | 93* | 90* | 90 | 93 | 93 |
| FP2 Reflectivity (%) | 86* | 86* | 86* | 80* | 80 | 86 | 86 |
| Parameters at ref. wavelength(s) | |||||||
| Strehl from optical design (%) | 97 | 96 | 93 | 92 | 93 | 97 | 97 |
| Strehl from pupil apodisation (%) | 96 | 96 | 96 | 97 | 96 | 95 | 97 |
| Unbroadened FWHM (pm) | 4.9 | 4.9 | 5.7 | 6.8 | 6.8 | 5.7 | 10.4 |
| Broadened FWHM (pm) | 5.7 | 5.7 | 6.9 | 7.9 | 7.9 | 6.7 | 11.4 |
| rms FWHM (pm) | 0.043 | 0.043 | 0.064 | 0.083 | 0.083 | 0.064 | 0.081 |
| rms wavelength shift (pm) | 1.6 | 1.6 | 1.6 | 2.1 | 2.1 | 1.6 | 2.1 |
| Peak FPI transmission (%) | 93.5 | 93.5 | 93.5 | 92.5 | 92.5 | 93.5 | 96.3 |
| rms Integrated transmission (%) | 6.6 | 6.6 | 6.4 | 7.5 | 7.5 | 6.4 | 3.8 |
| Parasitic light (%) | 0.75 | 0.75 | 0.79 | 1.0 | 1.0 | 0.79 | 0.77 |
| rms Parasitic light (%) | 0.062 | 0.062 | 0.062 | 0.096 | 0.096 | 0.062 | 0.033 |
| Prefilter FWHM (nm) | 0.43 | 0.43 | 0.43 | 0.28 | 0.28 | 0.43 | 0.80 |
Notes. The calculated parameters are based on the input parameters given in Table 1, optimisation of their optical design, numerical simulations, and optimisation of FPI parameters. The Strehl intensities based on apodisation effects and optical design limitations are calculated separately. * The reflectivities given are design values, which differ from the actual values.
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