FORS grism page
In the tables below we give the approximately constant dispersion only. The spectral resolution will depend on the wavelength and on the projected slit width which depends on the collimator.
FORS1 Standard Grisms
Presently the following grisms are available with FORS1. Response curves are given in the user manual. The response curves are also available as tables. The values shown are for the new E2V mosaic detector.
| Grism name + ESO number | Lambda Central | Wavelength range | Dispersion | Order separation |
|---|---|---|---|---|
| [nm] | [nm] | [Å/mm] | filter | |
| GRIS_600B+12 | 465 | 330 - 621 | 50 | none |
| GRIS_600V+94 | 585 | 443 - 737 | 49 | GG435 or GG375 |
| GRIS_600R+14 | 627 | 501 - 769 | 45 | GG435 |
| GRIS_300V+10 (1) | 590 | 330 - (660) | 112 | none |
| GRIS_300V+10 (1) | 590 | 385 - (750) | 112 | GG375 |
| GRIS_300V+10 | 590 | 445 - 865 | 112 | GG435 |
| GRIS_150I+17 (1) | 720 | 330 - (650) | 230 | none |
| GRIS_150I+17 (1) | 720 | 385 - (750) | 230 | GG375 |
| GRIS_150I+17 (1) | 720 | 445 - (870) | 230 | GG435 |
| GRIS_150I+17 | 720 | 600 - 1100 | 230 | OG590 |
| holographic: | ||||
| GRIS_1200B+97 | 435 | 366 - 511 | 24.0 | none |
| GRIS_1200g+96 | 488 | 417 - 564 | 24.3 | none |
(1) For these, if used without or with the listed order separation filter,
the orders overlap above the given wavelength.
FORS2 Standard Grisms
Starting in March 2002 the following grisms are available with FORS2. Efficiency curves are given in the user manual. The response curves are also available as tables.
| Grism name + ESO number | Lambda Central | Wavelength range (MIT) | Dispersion | Order separation |
|---|---|---|---|---|
| [nm] | [nm] | [Å/mm] | filter | |
| GRIS_600B+22 | 465 | 330 - 621 | 50 | none |
| GRIS_600I+25 | 795 | 663 - 939 | 44 | OG590 |
| GRIS_300V+20 (1) | 590 | 330 - (650) | 110 | none |
| GRIS_300V+20 (1) | 590 | 385 - (750) | 111 | GG375 |
| GRIS_300V+20 | 590 | 445 - 870 | 112 | GG435 |
| GRIS_300I+21 | 860 | 600 - 1100 | 108 | OG590 |
| GRIS_200I+28 | 745 | 560 - 1100 | 162 | OG550 (cemented) |
| GRIS_150I+27 (1) | 720 | 330 - (650) | 225 | none |
| GRIS_150I+27 (1) | 720 | 385 - (750) | 230 | GG375 |
| GRIS_150I+27 (1) | 720 | 445 - (880) | 230 | GG435 |
| GRIS_150I+27 | 720 | 600 - 1100 | 230 | OG590 |
| holographic: | ||||
| GRIS_1400V+18 (3) | 520 | 456 - 586 | 20.8 | none |
| GRIS_1200R+93 (3) | 650 | 575 - 731 | 25.0 | GG435 |
| GRIS_1028z+29 (3) | 860 | 773 - 948 | 28.3 | OG590 |
| GRIS_600RI+19 (3) | 678 | 512 - 845 | 55 | GG435 |
| GRIS_600z+23 (3) | 901 | 737 - 1070 | 54 | OG590 |
| 2nd order: | ||||
| GRIS_600I+25 (2) | 425 | 369 - 488 | 19 | FILT_465_250+82 |
| GRIS_600z+23 (2,3) | 466 | 389 - 546 | 20 | FILT_465_250+82 |
| (1) If used without or with the listed order separation filter, the orders will overlap above the given wavelength. | ||||
| (2) Second order - (the response table is out of date - measured for the old SITE detector) | ||||
| (3) Based on a volume phased holographic grating. | ||||
Identification of the arc lines
Please find a list of arc lines in the following table. There is no guaranty for the accuracy of the wavelengths. The optimum choice of lines will depend on the spectral resolution of the grisms and the data reduction method. In the long table for medium resolution grisms a preference column is included on the right hand side. Please have a look into the fits header for keyword INS.LAMP*.NAME and INS.LAMP*.TIME to see which lamps are on or off. In very rare cases broken lamps were not detected in time.
| low resolution | HeAr | down load |
|---|---|---|
| low resolution | HgCdHeAr | down load |
| medium resolution | HgCdHeNeAr | down load |
The following plots show the spectral line identification for the respective FORS1 (still with the old CCD) and FORS2 grisms. The relative line strength may change a lot since the switch on times for the lamps are changed from time to time. The 2nd order line identification plots are still to be prepared.
|
FORS1 Tek CCD postscript files: 1st order
2nd order
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FORS1 Tek CCD jpeg files: 1st order
2nd order
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FORS2 MIT-CCDs postscript files: 1st order
2nd order
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FORS2 MIT-CCDs jpeg files: 1st order
2nd order
|
