Tools and Tips
Catalogues of telluric standard stars:
- Hipparcos A1 stars or earlier, suitable for J, H, K, and L bands spectroscopy
- Hipparcos B8 or earlier with V <4.0 or B8 to G0 with V < 4.8, suitable for M-band spectroscopy
- Hipparcos O type stars (from ISAAC)
- Hipparcos B type stars (from ISAAC)
- Hipparcos G type stars (from ISAAC)
Catalogues of spectro-photometric standard stars:
- Calibration tables from NIST. This link provides wave numbers for a number of molecules, useful to calibrate CRIRES spectra either from atmosphericlines or with gas-cells. In wave number, CRIRES spectral range is [1850 - 10520]/cm. Currently, the installed gas-cells contain N2O and CO, respectively. A gas-cell containing OCS should be available in the near future.
- The wavelength calibration of CRIRES below 2500 nm is based on a Th-Arhollow cathode lamp. The wavelength standards in its emission line spectrum have been established in a collaboration between ESO and the US Institute of Standards and Technology (NIST): see Th Ar Atlas. If your research has benefited from the wavelength calibration we ask you to reference the corresponding paper Kerber, F., Nave, G. & Sansonetti, C.J 2008, ApJS178, 374: The Spectrum of Th-Ar Hollow Cathode Lamps in the 691-5804nm region: Establishing Wavelength Standards for the Calibration of Infrared Spectrographs in your publication.
- Additional line lists are part of the static calibration frames (19.3 MB). See the CRIRES calibration data for details.
For high observations aiming at high S/N, it is important to know if the quality of the flat-fields is a limiting factor. Following the May 2009 intervention, daily calibrations include 3 exposures for each wavelength setting observed during the night. Typical values for the S/N per pixel for the standard settings as defined in the P84.2 manuals can be seen at FF S/N/pixel . For free wavelength settings, values can be inferred from the closest standard settings.
The CRIRES pipeline is available for download.
Correction of non-linearity, including the odd-even effect:
Correcting both the flat-field and the science data from departure of linearity allows one to reduce the odd-even effect to an unnoticeable level. Static calibration files have been created that contain (amongst other files) the coefficients of the relation
I_corrected = [-b^2 +b^2 sqrt[1 - 4 c (a - I_orig)/b^2]]/(2 c)
for each pixel of each detector, where I_orig is the raw intensity after subtraction of the dark, and I_corrected is the intensity corrected for non-linear effects.
Note that data (including flat-field) obtained with a DIT < 2 s suffer from a different type of non-linear effects, caused by the finite reset time of the detector arrays. Therefore such DIT should be avoided. See science recipes , or more generally, the CRIRES pipeline: general description for more information.
Differential tracking allows to close the loop and/or to guide on an object that is moving relative to the target to be observed. Typical examples of the use of such a mode are:
- using a satellite of a planet as an AO guide star to observe a feature on the parent planet;
- using a (angularly small) planet, asteroid or comet to observe a feature moving relative to its optical photo-center;
- using a star as an AO guide star or SVGS to observe a planet, asteroid, comet passing in its vicinity.
Differential tracking is offered in service or visitor mode. However, some complicated programmes (for example observations of Jupiter whilst using one of its Moons to close the loop) are best performed in visitor mode. See Section 19 of the User Manual for details regarding this mode. When using HORIZONS you have to search for "VLT" in the "Observer location" and within the "Table Settings" output select RA/Dec and CSV format. The tool to transform JPL Horizons ephemeride files to PAF files required for P2PP is crossEphem2paf.tcl and requires tcl.
- tclsh crossEphem2paf.tcl -i sourceFileName -o fileName.paf
- tclsh crossEphem2paf.tcl -ra HHMMSS.SSSS -dec sddmmss.sss -o fileName.paf
- tclsh crossEphem2Paf.tcl -i fromHorizons.txt -o tracking.paf
- tclsh crossEphem2Paf.tcl -ra 112030.9517 -dec -031231.138 -o fixedCoord.paf
Examples of files:
- Original ephemerides file for Saturn , PAF file for Saturn
- Original ephemerides file for Rheaf, PAF file for Rhea
Note the extra column giving the distance between Rhea and Saturn in both the original ephemerides and PAF files. Also the PAF files contain the dates in ISO format.
Generic Tools and information
- ETC, Exposure Time Calculators
- Phase 1 Proposal Preparation and Submission
- Phase 2 Proposal Preparation for Service Mode observations
- Phase 2 p2pp
- NICMOS Units Converter
- Magnitude / Jansky Converter: Point Sources (ST-ECF NICMOS Tools )
- Magnitude / Jansky Converter: Extended Sources (ST-ECF NICMOS Tools )