Next: On-line reduction options during
Up: Using the FEROS software
Previous: Using the FEROS software
To use the automatic data reduction as described above, the DRS has to
be initialized at the beginning of the night.
For this purpose several flat-field and wavelength calibration
exposures have to be taken in the Object-Sky mode of FEROS
before the beginning of the night following the following sequence:
-
Reset the image catalogues FF.cat, ThAr.cat, Dark.cat,
Object.cat with the command @@ init ? reset
- Insert a new write-enabled DAT in the drive /dev/rmt/1m.
Note that this DAT will be overwritten from the beginning erasing
any previous contents! One 60m DAT can carry about 70 files. If you are
to take more than 70 full frames, it is advisable to change the
DAT before it is full.
-
Use the instrument control software XFCU running on the CCD control PC
next to the ISW to turn on the wavelength calibration lamp and use the
BIAS CCD control software to take several (typical 2) exposures of 15
sec each. For details on the XFCU software and the BIAS software see
the FEROS documentation. The resulting frames are automatically
transfered to the IWS and added to the catalogue ThAr.cat.
-
Switch with the XFCU program to the flatfield lamp and take, depending
on the S/N needed for a appropriate reduction of the planned science
exposures, 3 to 10 exposures of 30 sec. The frames are automatically
transfered to the IWS and added to the catalogue FF.cat.
- Initialize the DRS for the night with the command @@ init [guess]
where guess is the name of a previously saved guess session. Typically
this is the session saved in the night before. The session names are
formed automatically from the file number of the first calibration
exposure in the catalogue ThAr.cat and the prefix ThAr, e.g.,
ThAr0741.
Now the following initialization steps are performed
- Initialization of the session keywords and tables
(INIT/FEROS)
- Averaging of the frames of the respective catalogues
FF.cat, ThAr.cat.
- Setting of the CCD gain keyword according to descriptor
CCD_GAIN and the values specified in init.prg
- Definition of the echelle orders in the averaged flatfield
(DEFINE/FEROS); the fitted positions are shown in the
display window.
- Standard reduction of the flatfield
(BACKGR/FEROS, RECTIFY/FEROS, EXTRACT/FEROS).
The extraction is done twice: the first time, the cross-order
profiles are determined for an optimum extraction with
cosmic removal for the science exposures; the second time
the flatfield orders are extracted.
The name of the reduced flatfield is found in the keyword
FLAT_IMG.
- Standard reduction of the wavelength calibration
(BACKGR/FEROS, RECTIFY/FEROS, EXTRACT/FEROS).
The name of the reduced calibration is found in the
keyword WLC_IMG
- Search for emission lines in the reduced calibration frame
(SEARCH/FEROS).
- Wavelength calibration by iterative fitting of the dispersion
coefficients (CALIBRATE/FEROS). The resdiuals of the
individual lines are plotted over the order number. The spread
should not exceed an rms of 0.05 Å.
-
The session parameters are saved as session WLC_IMG.
With this step completed, the FEROS on-line DRS is initialized.
Every new incoming spectrum will be saved and reduced now as described
above.
Next: On-line reduction options during
Up: Using the FEROS software
Previous: Using the FEROS software
Petra Nass
1999-06-15