FORS1:
science files and recipes

• recipe name:FORS_S_IMG_SCIENCE
• input frames:SCIENCE_IMG
• associated templates: FORS1_img_obs_crsplit, FORS1_img_obs_exp,FORS1_img_occ_crsplit, FORS1_img_occ_exp

description: The incoming science frame is searched for overexposed pixels and some basic statistical parameters are determined. Then the science 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 used.
The luminosities of the objects on the image are now determined and stored in a photometry table . The image quality is determined and written to the QC1 Log. By means of the extinction coefficients table the science frame and the photometry table are flux calibrated.

products:

Reduced Science Frame	PS	GIF	Header
r.FORS1.2003-03-27T00:06:18.022_0000

• recipe name: FORS_S_LSS_SCISIMP
• input frames: SCIENCE_LSS
• associated templates: FORS1_lss_obs_exp , FORS1_lss_obs_exp_fast, FORS1_lss_obs_off, FORS1_lss_obs_off_fast

purpose: The incoming science frame is searched for overexposed pixels. The frame is then corrected for bias and dark if the appropriate frames are found in the set of reference frames or if a non zero bias and dark value is given by the first two values of CCDPAR respectively. If the third value of CCDPARis NO , the bias correction is performed by just subtracting a master bias image. If the third value of CCDPAR is 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 the third value of CCDPAR is 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.
The science frame is then divided by a normalized master flat field to remove pixel to pixel variations. Finally the science frame is remapped from pixel space to wavelength space by the application of the dispersion relation and is then rebinned to constant wavelength steps.
In the end the rebinned frame is searched for point source spectra. The sky background at the positions of the object spectra are fitted and subtracted. Now the spectra are extracted using the algorithm of Horne (Horne, 1986, PASP, 98, 609).

products:

Reduced Science Frame	PS	GIF	Header
r.FORS1.2003-03-26T00:46:13.245_0000

• recipe name: FORS_S_MOS_SCISIMP
• input frames: SCIENCE_MOS
• associated templates: FORS1_mos_obs_exp , FORS1_mos_obs_exp_fast, FORS1_mos_obs_off, FORS1_mos_obs_off_fast, FORS1_specphot_obs_exp_fast

purpose: The incoming science frame is searched for overexposed pixels. The frame is then corrected for bias and dark if the appropriate frames are found in the set of reference frames or if a non zero bias and dark value is given by the first two values of CCDPAR respectively. If the third value of CCDPARis NO , the bias correction is performed by just subtracting a master bias image. If the third value of CCDPAR is 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 the third value of CCDPAR is 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.
The science frame is then divided by a normalized master flat field to remove pixel to pixel variations. Finally the science frame is remapped from pixel space to wavelength space by the application of the dispersion relation and is then rebinned to constant wavelength steps.
In the end the rebinned frame is searched for point source spectra. The sky background at the positions of the object spectra are fitted and subtracted. Now the spectra are extracted using the algorithm of Horne (Horne, 1986, PASP, 98, 609).

products:

Reduced Science Frame	PS	GIF	Header
r.FORS1.2003-04-04T06:42:57.302_0000

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