Offered spectroscopic modes
Spectroscopy can be performed using one of 4 offered grisms or a prism.
The resolution quoted here have been computed for the 86mas slit.
The spectral resolution for slitless spectroscopy and spectrum taken with the 172mas slit is set by the PSF.
Prism spectroscopy is offered again since P87 in VM only.
Grism spectroscopy is offered in both VM and SM as of P86.
Arc spectra with the long wavelength modes are not possible.
Spectroscopic modes associated with the grisms
| Mode Name | Camera Name | Order | Spectral Range | Linear Dispersion | Resolution | Arc Atlas |
| S54_4_SJ | S54 | 1 | 0.91-1.40 | 2.00 | 400 | S54_4_SJ_wc.pdf |
| S54_3_SH | S54 | 3 | 1.37-1.84 | 0.69 | 1500 | S54_3_SH_wc.pdf |
| S27_3_SH | S27 | 3 | 1.37-1.72 | 0.34 | 1500 | Not available |
| S27_4_SH | S27 | 1 | 1.37-1.84 | 0.97 | 500 | S27_4_SH_wc.pdf |
| S54_2_SK | S54 | 2 | 1.79-2.42 | 0.97 | 1400 | S54_2_SK_wc.pdf |
| S27_2_SK | S27 | 2 | 1.79-2.24 | 0.59 | 1400 | S27_2_SK_wc.pdf |
| S54_3_SK | S54 | 2 | 1.79-2.57 | 1.00 | 1400 | S54_3_SK_wc.pdf |
| S27_3_SK | S27 | 2 | 2.02-2.53 | 0.50 | 1400 | S27_3_SK_wc.pdf |
| S54_4_SK | S54 | 1 | 1.79-2.57 | 1.96 | 700 | S54_4_SK_wc.pdf |
| L27_1_L | L27 | 2 | 3.20-3.76 | 1.60 | 700 | Not available |
| L54_2_L | L54 | 1 | 3.20-3.76 | 2.00 | 1100 | Not available |
| L27_1_LP | L27 | 2 | 3.50-4.10 | 1.60 | 700 | Not available |
| L54_2_LP | L54 | 1 | 3.50-4.10 | 2.00 | 1100 | Not available |
| L27_2_LP | L27 | 1 | 3.50-4.10 | 1.00 | 1100 | Not available |
| S54_4_SHK | S54 | 1 | 1.30-2.60 | 1.94 | 550 | S54_4_SHK.pdf |
| L54_1_SL | L54 | 2 | 2.60-4.20 | 3.16 | 700 | Not available |
| L27_1_SL | L27 | 2 | 2.60-4.10 | 1.57 | 700 | Not available |
| L54_2_SL | L54 | 1 | 3.02-4.20 | 2.01 | 1100 | Not available |
| L27_2_SL | L27 | 1 | 3.47-4.20 | 1.00 | 1100 | Not available |
List of Argon Lines in calibration arcs
Spectroscopic modes associated with the prism
| Mode Name | Filter | Dispersion (nm/pixel) |
Fit validity (μm) |
Wavelength range (μm) | Resolution | Fit order | Fit rms (nm) |
| L27_P1 | None | 8.5 | 1 - 4 | 0.85 - 5.5 | 90 | 3 | 10 |
| L27_P1 | None | 6.3 | 4.5 - 5.5 | 0.85 - 5.5 | 250 | 5 | 2.9 |
| S13_P1 | CutOff_2.5um | 4.1 | - | 0.85 - 2.5 | 60 | 3 | 10 |
| S27_P1 | CutOff_2.5um | 8.2 | - | 0.85 - 2.5 | 60 | - | - |
Transmission curve for the Cutoff 2.5 micron filter used to select the not-thermal wavelength range with the prims.
In order to get an idea of the performance of this mode, an example spectrum (DIT=0.5, 86mas slit) of a red 2MASS star with J=8.04, H=7.20 and K=7.01 is provided (courtesy C. Lidman).
Raw data in two nod positions:
Spectrum nod A
Spectrum nod B
Subtracted frame: Spectrum: nod A - nod B