FORS2:
calibration files and recipes

• recipe name: FORS_S_GEN_MASTER_BIAS
• input frames: BIAS
• associated templates: FORS2_img_cal_bias

description: Each input frame is bad pixel corrected. Then the master frame is calculated as the mean (AVMODE = 1) or median ( AVMODE = 2) of the stack of input frames. Iteratively each input frame is compared with the master frame for large deviations. If one frame differs too much it is removed from the set of input frames and a new master is produced. As soon as no frame has to be rejected the final master frame has been found. The rejection limits are given by the THRESH parameter.
The median process is modified in that way that instead of the median the mean of all values in an interval centered on the median is taken. A master frame is generated only if MIN_COUNT raw frames are remaining for the averaging process. This ensures a minimum quality of the product.
At the end, the new master frame is compared with the corresponding certified master frame from the calibration database.

products:

Master	PS	GIF	Header
F2_MBIA_021001A_C1hi_2x2
F2_MBIA_021001A_C2hi_2x2

• recipe name: FORS_S_GEN_MASTER_DARK
• input frames: DARK
• associated templates: FORS2_img_cal_dark

description: First the individual input frames are corrected for bias and bad pixels, after that the frames are combined to create the (preliminary) master. Both processes are controlled by the keyword AVMODE, which is a two--digit integer. If the first digit is 0, the bias correction is performed by just subtracting a master bias image. If the first digit is 1, the bias correction is performed using the scaled master bias. The scaling is done as follows: Each of the sections of the master bias is divided by its median and multiplied by the median of the corresponding pre-/overscan region of the input frame. If the first digit is 2, the master bias is also scaled, but each of the sections of the master bias is divided by the median of its corresponding pre-/overscan region and multiplied by the median of the pre-/overscan region of the input frame.
The second digit of AVMODE controls the averaging process. If it is 0, the generated master is the average of the means of the input frames and hence constant, if it is 1, the master frame is calculated as the mean, if it is 2 as the median of the stack of input frames.
Iteratively each input frame is compared with the master frame for large deviations. If one frame differs too much it is removed from the set of input frames and a new master is produced. As soon as no frame has to be rejected the final master frame has been found. The rejection limits are given by the THRESH parameter.
The median process is modified in that way that instead of the median the mean of all values in an interval centered on the median is taken. Each input frame is bad pixel corrected in advance.
A master frame is generated only if MIN_COUNT raw frames are remaining for the averaging process. This ensures a minimum quality of the product.
At the end, the new master frame is compared with the certified master frame from the calibration database.

products:

Master	PS	GIF	Header
F2_MDRK_021110A_C1hi_2x2
F2_MDRK_021130A_C2hi_2x2

• recipe name: FORS_S_IMG_MASTER_SKYFLAT
• input frames: SKY_FLAT_IMG
• associated templates: FORS2_img_cal_skyflat

description: Before the master is generated each twilight flat is checked for overexposure. If more than MAXOV percent of the pixels of a frame are overexposed it is not used for the master process.
Then the individual input frames are corrected for bias, dark and bad pixels, after that the frames are combined to create the (preliminary) master. Both processes are controlled by the keyword AVMODE, which is a two--digit integer. If the first digit is 0, the bias correction is performed by just subtracting a master bias image. If the first digit is 1, the bias correction is performed using the scaled master bias. The scaling is done as follows: Each of the sections of the master bias is divided by its median and multiplied by the median of the corresponding pre-/overscan region of the input frame. If the first digit is 2, the master bias is also scaled, but each of the sections of the master bias is divided by the median of its corresponding pre-/overscan region and multiplied by the median of the pre-/overscan region of the input frame.
Iteratively each input frame is compared with the master frame for large deviations. If one frame differs too much it is removed from the set of input frames and a new master is produced. As soon as no frame has to be rejected the final master frame has been found. The rejection limits are given by the THRESH parameter.
The median process is modified in that way that instead of the median the mean of all values in an interval centered on the median is taken. Each input frame is bad pixel corrected in advance.
A master frame is generated only if MIN_COUNTraw frames are remaining for the averaging process. This ensures a minimum quality of the product.
At the end, the new master frame is compared with the corresponding certified master frame from the calibration database.

products:

Master	PS	GIF	Header
F2_MKFI_021001A_BBE_C1lo_2x2s
F2_MKFI_021001A_BBE_C2lo_2x2s
F2_MKFI_021001A_IBE_C1lo_2x2s
F2_MKFI_021001A_IBE_C2lo_2x2s
F2_MKFI_021001A_RSp_C1lo_2x2s
F2_MKFI_021001A_RSp_C2lo_2x2s
F2_MKFI_021001A_VBE_C1lo_2x2s
F2_MKFI_021001A_VBE_C2lo_2x2s
F2_MKFI_021003A_USp_C1lo_2x2s
F2_MKFI_021003A_USp_C2lo_2x2s

• recipe name:FORS_S_IMG_MASTER_SCRFLAT
• input frames:SCREEN_FLAT_IMG
• associated templates: FORS2_img_cal_scrflat

description: Before the master is generated each screen flat is checked for overexposure. If more than MAXOV percent of the pixels of a frame are overexposed it is not used for the master process.
Then the individual input frames are corrected for bias, dark and bad pixels, after that the frames are combined to create the (preliminary) master. Both processes are controlled by the keyword AVMODE, which is a two--digit integer. If the first digit is 0, the bias correction is performed by just subtracting a master bias image. If the first digit is 1, the bias correction is performed using the scaled master bias. The scaling is done as follows: Each of the sections of the master bias is divided by its median and multiplied by the median of the corresponding pre-/overscan region of the input frame. If the first digit is 2, the master bias is also scaled, but each of the sections of the master bias is divided by the median of its corresponding pre-/overscan region and multiplied by the median of the pre-/overscan region of the input frame.
Iteratively each input frame is compared with the master frame for large deviations. If one frame differs too much it is removed from the set of input frames and a new master is produced. As soon as no frame has to be rejected the final master frame has been found. The rejection limits are given by the THRESH parameter.
The median process is modified in that way that instead of the median the mean of all values in an interval centered on the median is taken. Each input frame is bad pixel corrected in advance.
A master frame is generated only if MIN_COUNT raw frames are remaining for the averaging process. This ensures a minimum quality of the product.
At the end, the new master frame is compared with the corresponding certified master frame from the calibration database.

products:

Master	PS	GIF	Header
F2_MSFI_021001A_BBE_C1lo_2x2s
F2_MSFI_021001A_BBE_C2lo_2x2s
F2_MSFI_021001A_IBE_C1lo_2x2s
F2_MSFI_021001A_IBE_C2lo_2x2s
F2_MSFI_021001A_RSp_C1lo_2x2s
F2_MSFI_021001A_RSp_C2lo_2x2s
F2_MSFI_021001A_USp_C1lo_2x2s
F2_MSFI_021001A_USp_C2lo_2x2s
F2_MSFI_021001A_VBE_C1lo_2x2s
F2_MSFI_021001A_VBE_C2lo_2x2s

• recipe name:FORS_S_IMG_MASTER_NIGHTFLAT
• input frames: SCIENCE_IMG
• associated templates: FORS2_img_obs_crsplit, FORS2_img_obs_exp, FORS2_img_occ_crsplit, FORS2_img_occ_exp

description: Before the master is generated each night sky flat is checked for overexposure. If more than MAXOV percent of the pixels of a frame are overexposed it is not used for the master process.
Then the individual input frames are corrected for bias, dark and bad pixels, after that the frames are combined to create the (preliminary) master. Both processes are controlled by the keyword AVMODE, which is a two--digit integer. If the first digit is 0, the bias correction is performed by just subtracting a master bias image. If the first digit is 1, the bias correction is performed using the scaled master bias. The scaling is done as follows: Each of the sections of the master bias is divided by its median and multiplied by the median of the corresponding pre-/overscan region of the input frame. If the first digit is 2, the master bias is also scaled, but each of the sections of the master bias is divided by the median of its corresponding pre-/overscan region and multiplied by the median of the pre-/overscan region of the input frame.
Iteratively each input frame is compared with the master frame for large deviations. If one frame differs too much it is removed from the set of input frames and a new master is produced. As soon as no frame has to be rejected the final master frame has been found. The rejection limits are given by the THRESH parameter.
The median process is modified in that way that instead of the median the mean of all values in an interval centered on the median is taken. Each input frame is bad pixel corrected in advance.
A master frame is generated only if MIN_COUNT raw frames are remaining for the averaging process. This ensures a minimum quality of the product. At the end, the new master frame is compared with the corresponding certified master frame from the calibration database.

• recipe:FORS_S_IMG_STDSTAR
• input frames: STANDARD_IMG
• associated templates: FORS2_img_obs_crstd, FORS2_img_obs_std

description: The incoming standard star frame is searched for overexposed pixels. Some basic statistical parameters are determined. Then the standard star frame goes through a standard reduction procedure, i.e.\ bad pixel, bias and dark correction as well as flatfielding. All these operations are done in case an appropriate calibration frame is present in the set of reference frames. If SCALE=NO, the bias correction is performed by just subtracting a master bias image. If SCALE=MED, the bias correction is performed using the scaled master bias. The scaling is done as follows: Each of the sections of the master bias is divided by its median and multiplied by the median of the corresponding pre-/overscan region of the input frame. If SCALE=OVE, the master bias is also scaled, but each of the sections of the master bias is divided by the median of its corresponding pre-/overscan region and multiplied by the median of the pre-/overscan region of the input frame. Alternatively to the master bias and master dark images constant values ( BIAS_CONS , DARK_CONS ) may be subtracted.
The luminosities of the objects on the image are now determined and stored in a photometry table (see recipe FORS_IMG_OBS_PHOTOMETRYfor details). This table is aligned with a standard star reference catalog. The parameter POINTACC defines the search radius for the catalog search. Only objects within a radius POINTACC around a catalog position are potential matches. If there is more than one coincidence for a catalog object the catalog magnitude is compared with the measured values and the best match is used. Object magnitudes are estimated by means of an already existing extinction coefficients table if there is any, otherwise are computed using default extinction coefficients.
These aligned photometry tables can be used to determine zeropoints, extinction and color coefficients using the recipe FORS_IMG_CAL_CALCOEFF .

• recipe name: FORS_S_LSS_NORMFLAT
• input frames: SCREEN_FLAT_LSS
• associated templates: FORS2_lss_cal_scrflat

description: Before the master is generated each screen flat is checked for overexposure. If more than MAXOVER percent of the pixels of a frame are overexposed it is not used for the master process.
Then the individual input frames are corrected for bias, dark and bad pixels, after that the frames are combined to create the (preliminary) master. Both processes are controlled by the keyword AVMODE, which is a two--digit integer. If the first digit is 0, the bias correction is performed by just subtracting a master bias image. If the first digit is 1, the bias correction is performed using the scaled master bias. The scaling is done as follows: Each of the sections of the master bias is divided by its median and multiplied by the median of the corresponding pre-/overscan region of the input frame. If the first digit is 2, the master bias is also scaled, but each of the sections of the master bias is divided by the median of its corresponding pre-/overscan region and multiplied by the median of the pre-/overscan region of the input frame.
The median process is modfied in that way that instead of the median the mean of all values in an interval centered on the median is taken. Each input frame is bad pixel corrected in advance.
A master frame is generated only if MIN_COUNT raw frames are remaining for the averaging process. This ensures a minimum quality of the product.
A polynomial fit or a median filter is then used to model the large scale structure of the created master flat field frame along the dispersion axis. The master flat field frame is finally divided by this smoothed version and results in a frame of the high frequency variations in the master flat field (detector pixel to pixel variations). The smoothing method and the associated parameter can be may be adjusted in the pipeline setup tables ( DRS_SETUP_LSS ).
Finally the normalized flat field is compared with a corresponding, certified version from the calibration data base.

products:

Master	PS	GIF	Header
F2_MSFL_021014A_G600B_S10F__L1C1hi_2x2s
F2_MSFL_021014A_G600B_S10F__L1C2hi_2x2s
F2_MSFL_021106A_G300I_S10OG590L1C1hi_2x2s
F2_MSFL_021106A_G300I_S10OG590L1C2hi_2x2s
F2_MSFL_021129A_G150I_S07F__L1C1hi_2x2s
F2_MSFL_021129A_G150I_S07F__L1C2hi_2x2s
F2_MSFL_021213A_G300V_S10F__L1C1hi_2x2s
F2_MSFL_021213A_G300V_S10F__L1C2hi_2x2s
F2_MSFL_030415A_G1028z_S10OG590L0C1hi_2x2s
F2_MSFL_030415A_G1028z_S10OG590L0C2hi_2x2s
F2_MSFL_030415A_G200I_S10F__L0C1hi_2x2s
F2_MSFL_030415A_G200I_S10F__L0C2hi_2x2s

• recipe name: FORS_S_LSS_WAVE
• input frames: LAMP_LSS
• associated templates: FORS2_lss_cal_wave

description: The incoming comparison spectrum frame is checked with respect to the number of overexposed pixels. The comparison spectrum is searched for emission lines which are identified using the optical parameters of the FORS grisms. The identified lines are used to perform a two-dimensional modelling of the dispersion relation.

• recipe name: FORS_S_MOS_NORMFLAT
• input frames: SCREEN_FLAT_MOS
• associated templates: FORS2_MOS_cal_scrflat

description: Before the master is generated each screen flat is checked for overexposure. If more than MAXOVER percent of the pixels of a frame are overexposed it is not used for the master process.
Then the individual input frames are corrected for bias, dark and bad pixels, after that the frames are combined to create the (preliminary) master. Both processes are controlled by the keyword AVMODE, which is a two--digit integer. If the first digit is 0, the bias correction is performed by just subtracting a master bias image. If the first digit is 1, the bias correction is performed using the scaled master bias. The scaling is done as follows: Each of the sections of the master bias is divided by its median and multiplied by the median of the corresponding pre-/overscan region of the input frame. If the first digit is 2, the master bias is also scaled, but each of the sections of the master bias is divided by the median of its corresponding pre-/overscan region and multiplied by the median of the pre-/overscan region of the input frame.
The median process is modfied in that way that instead of the median the mean of all values in an interval centered on the median is taken. Each input frame is bad pixel corrected in advance.
A master frame is generated only if MIN_COUNT raw frames are remaining for the averaging process. This ensures a minimum quality of the product.
A polynomial fit or a median filter is then used to model the large scale structure of the created master flat field frame along the dispersion axis. The master flat field frame is finally divided by this smoothed version and results in a frame of the high frequency variations in the master flat field (detector pixel to pixel variations). The smoothing method and the associated parameter can be may be adjusted in the pipeline setup tables ( DRS_SETUP_MOS ).
Finally the normalized flat field is compared with a corresponding, certified version from the calibration data base.

products:

Master	PS	GIF	Header
F2_MSFM_021223A_G600B_Sm3606F__L0C1hi_2x2s
F2_MSFM_021223A_G600B_Sm3606F__L0C2hi_2x2s
F2_MSFM_021224A_G1028z_Sm1237OG590L0C1hi_2x2s
F2_MSFM_021224A_G1028z_Sm1237OG590L0C2hi_2x2s
F2_MSFM_030406A_G300V_Sp11706F__L1C1hi_2x2s
F2_MSFM_030406A_G300V_Sp11706F__L1C2hi_2x2s
F2_MSFM_030415A_G200I_S0F__L0C1hi_2x2s
F2_MSFM_030415A_G200I_S0F__L0C2hi_2x2s
F2_MSFM_030415A_G600I_S0OG590L0C1hi_2x2s
F2_MSFM_030415A_G600I_S0OG590L0C2hi_2x2s
F2_MSFM_030421A_G300I_S0F__L0C1hi_2x2s
F2_MSFM_030421A_G300I_S0F__L0C2hi_2x2s

• recipe name: FORS_S_MOS_WAVE
• input frames: LAMP_MOS
• associated templates: FORS2_MOS_cal_wave

description: The incoming comparison spectrum frame is checked with respect to the number of overexposed pixels. The comparison spectrum is searched for emission lines which are identified using the optical parameters of the FORS grisms. The identified lines are used to perform a two-dimensional modelling of the dispersion relation.

Send comments to <smoehler@eso.org>  Last update: Jan 22, 2000