Tools and Tips

CRIRES-specific tools

Catalogues of telluric standard stars:

Catalogues of spectro-photometric standard stars:

Optical Spectrophotometric Standards of SpT B4-A9. Models for these stars in the range 950 to 5466 nm are collected in this gzipped FITS binary file, part of the static calibration frames (19.3 MB).

Line lists

CRIRES flat-field

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.

CRIRES pipeline

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

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.

Usage:

  • tclsh crossEphem2paf.tcl -i sourceFileName -o fileName.paf
  • tclsh crossEphem2paf.tcl -ra HHMMSS.SSSS -dec sddmmss.sss -o fileName.paf

Examples:

  • tclsh crossEphem2Paf.tcl -i fromHorizons.txt -o tracking.paf
  • tclsh crossEphem2Paf.tcl -ra 112030.9517 -dec -031231.138 -o fixedCoord.paf

Examples of files:

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