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.

FORS2 standard grisms

The following grisms form the Standard Instrument Configuration. Response curves are given in the User Manual.

Grism name + ESO number Lambda Central Wavelength range Dispersion Order separation
  [nm] [nm] [Å/mm] filter
standard:
GRIS_600B+22 465 330 - 621 50 none
GRIS_300V+10 (1) 590 330 - (660) 112 none
GRIS_300V+10 590 445 - 865 112 GG435
GRIS_300I+11 860 600 - 1100 108 OG590
GRIS_150I+27 (1) 720 330 - (650) 225 none
GRIS_150I+27 (1) 720 445 - (880) 230 GG435
GRIS_150I+27 720 600 - 1100 230 OG590
holographic:
GRIS_1400V+18 520 456 - 586 20.8 none
GRIS_1200B+97 435 366 - 511 24.0 none
GRIS_1200R+93 650 575 - 731 25.0 GG435
GRIS_1028z+29 860 773 - 948 28.3 OG590
GRIS_600RI+19 678 512 - 845 55 GG435
GRIS_600z+23 901 737 - 1070 54 OG590
 
(1) If used without or with the listed order separation filter, the orders will overlap above the given wavelength.

Identification of the arc lines

Please find a list of arc lines in the following table. There is noguaranty 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 fitsheader for keyword INS.LAMP*.NAME and INS.LAMP*.TIME to see which lampsare 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.The relative line strength maychange a lot since the switch on times for the lamps are changedfrom time to time. The 2nd order line identification plots are still tobe prepared.

Line identifications for FORS1 grisms (still with the old CCD) are given as well, to help with the reduction of old data.

FORS1 Tek CCD
postscript files:

1st order

2nd order

  • not offered
  • not offered
FORS1 Tek CCD
jpeg files:

1st order

2nd order

  • not offered
  • not offered
FORS2 MIT-CCDs
postscript files:

1st order

2nd order

  • GRIS_600I
  • GRIS_600z+23
FORS2 MIT-CCDs
jpeg files:

1st order

2nd order

  • GRIS_600I
  • GRIS_600z+23