|Space Telescope Science Institute|
|COS Instrument Handbook|
Table 5.4 and Table 5.5 show the wavelength ranges recorded on the detectors for each valid combination of grating and central-wavelength setting at the nominal FP-POS=3 position (Section 5.8.2). The wavelength ranges spanned at other FP-POS settings may be estimated using the FP-POS step values provided in Chapter 13. Note, however, that uncertainties in the positioning of the Optics Select Mechanisms (Section 3.1.3) correspond to about half of an FP-POS step. These wavelength ranges are subject to change as the instrumental calibration evolves. The most recent measurements are available from the COS Web site.Table 5.4: Wavelength Ranges for FUV Gratings for FP-POS=3
Recorded wavelengths2 1118 – 22513
The central wavelength is (approximately) the shortest wavelength recorded on segment A.
All wavelength ranges quoted here are approximate, due to uncertainties in the position of the OSM1 mechanism.
G140L spectra are flux calibrated up to 2150 Å. At longer wavelengths, second-order light may be present (Section 5.1.3).
Table 5.5: Wavelength Ranges for NUV Gratings for FP-POS=3
1334 – 17332 1768 – 19673 2059 – 24584 3161 – 35605
For central wavelength 2635 Å, the stripe A wavelengths are listed for completeness only (and in case a bright emission line falls onto the detector). The NUV detector’s sensitivity at these wavelengths is extremely low. To obtain a low-resolution spectrum at wavelengths below ~ 1700 Å, we recommend the FUV grating G140L.
The values in shaded cells are wavelength ranges observed in second order. Their dispersion is twice that of the first-order spectrum. First-order flux, from wavelengths twice those of the listed range, will be present at the ~ 5% level.
Lyman α may be present in second order.
Longward of 3200 Å, second-order light may be present. At these wavelengths, the flux calibration applied by calcos is unreliable (Section 5.1.3).