Data Reduction Frequently Asked Questions
List of FAQs
The search will be performed in the questions and answers.
General
- What is the best way to reduce my VLT data?
- What operating systems are supported by the pipelines?
- How do I retrieve the pipeline version used to generate a product file?
- Where do I find reference data (e.g. line catalogs, configuration tables, etc.)?
- How do I find out the exposure time for a given observation?
- The calibration data for my observations look strange. Can you confirm that they look as the are supposed to look?
- I derived quantities related to the performance of an instrument. How do I know whether these numbers are "normal"?
Reflex
- What is the advantage of Reflex over other ways to run the pipeline?
- What documentation is available for Reflex?
- How do I install a pipeline in Reflex?
- I have updated my EsoReflex installation and when I run esoreflex it behaves weirdly (aborts or hangs or gives strange error messages). How can I fix this problem?
- How do I learn how to run a the Reflex workflow for my instrument?
- What are the system requirements to install Reflex?
- I tried to Open (or Configure) an Actor while the workflow is running and now it does not react any more. What should I do?
- In order to organize my data I had to increase the maximum memory for java. This memory stays in use and slows down other processes also when the workflow is not running. Is there a way to free the memory without exiting Reflex/Kepler?
- The content of a data set has changed but the Data Organizer marks it as processed "OK" - why?
- How do I customize the data reduction chain of a EsoReflex workflow by including external scripts?
- How do I install Python dependencies for ESOReflex using conda?
Gasgano
- What documentation is available for Gasgano?
- What do I do if I get the messaged "CPL initialisation failed" in gasgano?
- I successfully ran the installation script to install the pipeline, but when I try to run gasgano I get the following error:...
- Gasgano hangs when adding new files, what do I do?
- What do I do if recipe fails because frames are not classified?
- The pipeline cannot find recipe files, what is the problem?
Instrument specific FAQs
- AMBER
- APEX
- Are there any pipelines available to reduce APEX heterodyne data (instruments SHFI, FLASH, CHAMP+, SEPIA and PI230)?
- Are there any pipilines available to reduce APEX bolometer data (instruments LABOCA, SABOCA & Artemis)?
- Where can I find calibration files for the APEX bolometer instruments LABOCA and SABOCA?
- CRIRES
- Are there any known problems with CRIRES data?
- How can I read in CRIRES reduced data using IDL or IRAF?
- Is there a script to associate science and calibration data, create master frames and do the data reduction?
- I have two objects in the CRIRES slit, and I want to extract both spectra, how do I do it?
- I have a very low S/N spectrum and/or just emission lines, how can I reduce my spectra?
- There are few ThAr lines in my wavelength calibration spectra, what do I do?
- How do I plot my reduced spectra?
- Can I run the ESO CRIRES pipeline with MacOS?
- ESPRESSO
- I can run the whole pipeline and produce end products, but I can not do so in interactive mode. Am I doing something wrong, or is there a way to get it to run interactively?
- Is there a way to manually set the parameters of the CCF computation? In particular, what is the default range of radial velocity values that is being searched? And how can I change these?
- I've had some trouble extracting a good RV value through Esoreflex for some spectra. A quick look at the CCF shows no line, or a line with different properties than expected, while a quick glance at the spectrum suggests it looks reasonable. Any idea what is going on here and how to fix this?
- Is a rv_step of 0.5 too wide for a precise RV extraction? What would a good step size be?
- What is the list of supported stellar types?
- Do I need to specify anywhere the binning mode and source on fibre B when running EsoReflex?
- Are there any other settings than rv_center, rv_range, rv_step to pay attention to, or to change, when running EsoReflex to achieve the highest possible precision of RV?
- I found that I obtain very different RV values for different spectral templates/masks of the order of several hundred m/s. Is this normal?
- Should I expect the FWHM of the cross-correlation function (CCF) of ESPRESSO to be smaller than that of HARPS on the same target, due to ESPRESSO's higher resolution?
- The esprd_sci_red recipe crashes, but all the input files and parameters seem ok. What happened?
- What do I have to take care of if I want to compute the radial velocity of the same target over a certain period of time? And which precision can I expect?
- FLAMES/GIRAFFE
- FORS1/FORS2
- Are there any known problems with FORS1 data?
- Are there any known problems with FORS2 data?
- What is the best way to reduce FORS2 data?
- I have downloaded some FORS2 data from the archive. Why are there multiple fits files with the same start-time?
- I activated the "Use CalSelector Associations" option in the DataOrganizer. Now I get an error even though the Datasets were marked as complete. Why?
- How can I find the photometric zero point for my FORS images?
- When I run the fors_zeropoint recipe, it gives me the warning that no star can be found because of missing WCS functionalities. Should I be concerned?
- Where can I find a line-list to use for the wavelength calibration of my data?
- My reduced spectra do not cover the wavelength range I expected - why?
- Why do I get the message that "no slits could be detected", even though in the raw frames I can clearly see the slits?
- In order to observe the range 4100-6800 Å with GRIS_600B+22, we have shifted the slit itself. A bright feature appears in the spectrum. What is it?
- There is no flux standard star for my LSS observations - why?
- Why do my flux-calibrated spectra not agree with independent photometric measurements?
- In reducing some FORS2 MXU spectra, we are using a star which was observed in MOS mode to flux-calibrate the spectra. For chip1, everything is OK, but chip 2 fails. Why?
- Why are my spectra not flux calibrated, even though there are standard star observations in the data set?
- Although I am experimenting with different flux standard stars for my observation the flux calibrated spectra do not change. Why?
- There is no master response curve in my datasets - why?
- How does the pipeline choose where on the slit to extract the spectrum in long-slit mode?
- In reducing data from my MXU mask with overlapping spectra, slit tracing fails for a number of slitlets. What do I do?
- My target is faint and is not detected by the automatic detection algorithm for objects within the slit included in the pipeline.
How can I change the detection threshold in the pipeline? - The sky subtraction of my long slit spectra seems to be poor. What can I do?
- I prefer to subtract the sky with external routines (i.e. in the case of extended objects that cover most of the slit(s), or dedicated sky observations).
What are the relevant files I should use for this purpose? - I see a systematic offset in the coordinates determined for my extracted spectra with respect to the known coordinates of my objects - why?
General
Photometry
Spectroscopy (LSS/MOS/MXU)
Spectroscopy - Flux Calibration
Spectroscopy - Sky Subtraction and Spectra Extraction
- HAWK-I
- Are there any known problems with HAWK-I data?
- I have a problem with the HAWK-I pipeline. What should I do?
- How can we reach tenth of a magnitude accuracy in photometry?
- How good is HAWK-I astrometry?
- Are there any colour transformations available for the HAWK-I filters and another filter system?
- I get an unusual error when processing a large set of HAWK-I frames.
- ISAAC
- KMOS
- MIDI
- MUSE
- NACO
- Are there any known problems with NACO data?
- I am trying to reduce NACO data and found that my FowlerNsamp dark frames are negative. Is there any recommended procedure to subtract the dark from the flatfield frames in this mode? Is the dark current insignificant that it does not make a difference if it is not subtracted?
- SINFONI
- Are there any known problems with SINFONI data?
- What is the best way to reduce SINFONI data?
- Which pipeline data product are the important ones for quick inspection?
- Why is it that sometimes the pipeline only produces individual cubes but not the final co-added cube or the 2-D co-added image?
- How do I combine the individual 3-D cubes into a final mosaic?
- What software can I use to quickly visualise SINFONI reduced data?
- There seems to be an extraneous signal in my science image. Where does this come from?
- I still see sky lines in my reduced data, why?
- The pipeline fails with an error similar to: Standard error: [ERROR] sinfo_rec_distortion: parsing cpl input etc. What is wrong, and how can I proceed?
- SOFI
- SPHERE
- I do not have OBJECT,CENTER observations - can I use the bright spot near the center of the coronagraph as object position?
- Are there any colour transformations available for the SPHERE filters and another filter system?
- The pipeline does not detect the waffle spots in my K-band data.
- The pipeline identifies too many supposedly bad pixels in my K-band data.
- My science products show dark blobs in their background region.
- The wavelength calibration fails with default parameters.
- sph_zpl_star_center_img or sph_zpl_star_center_pol fails.
- My science result looks smeared out.
- I get an implausible polarimetric angle from my science products.
IRDIS Imaging (CI, DBI, DPI)
IRDIS Spectroscopy
ZIMPOL
- UVES
- Where can I find the science-ready data products available for UVES, and more information about their processing?
- What is the best way to reduce UVES data?
- Is there a way to generate a calibrated 2D spectrum with the pipeline?
- I see unexpected boxy emission-like features in my REDL spectra - where do they come from?
- I have a standard star in my DataSet but it is not found in the standard star catalog. Why?
- The response curve derived from my standard star looks very bad and the raw response shows huge residuals. Why?
- I activated the "Use CalSelector Associations" option in the DataOrganizer. Now I get an error even though the Datasets were marked as complete. Why?
- VIMOS
- Are there any known problems with VIMOS data?
- What is the best way to reduce VIMOS data?
- I activated the "Use CalSelector Associations" option in the DataOrganizer. Now I get an error even though the Datasets were marked as complete. Why?
- How can I be sure that my fibres are correctly labeled?
- Are there any colour transformations available for the VIMOS imaging filters and another filter system?
- I see small dark and bright regions in my normalized flat field - why?
- I want to process MOS data of the same target from different nights together - how can I do that?
- My MR+GG475 data show strong absorption features below 6000 Å. Where do they come from and how can I correct them?
- The spectrum of my MOS flux standard star is shifted in wavelength by several pixels. Why is that and how can I correct for it?
- My rectified and wavelength calibrated data show regions of negative flux adjacent to bright spectra and the 1D spectra look quite bad. How can I fix that?
- The flux level of my flux-calibrated data differs substantially if I use daytime flat fields instead of the attached night time flat fields. Why?
General
IFU
Imaging
MOS
- VISIR (pre-upgrade)
- VISTA/VIRCAM
- VST/OmegaCAM
- Are there any known problems with OmegaCAM data?
- Where can I download the OmegaCAM pipeline to reduce my data?
- My data shows an extended, bright feature - what can this be?
- A number of OmegaCAM filters show vignetting in their central regions. What are the causes for this and what are the dimensions of these features?
- Some OmegaCAM detectors show an odd central stripe in the bias and master bias images.
- X-Shooter
- Where can I find the science-ready data products available for X-Shooter, and more information about their processing?
- Are there any known problems with X-Shooter data?
- What is the best way to reduce X-Shooter data?
- I heard about problems with the X-shooter wavelength calibration. Where can I find more information?
- Processing of my NIR daytime calibration data fails - why?
- The MERGE2D spectrum shows lots of bad pixels. Why?
- Negative pixel values in the 2D spectrum image are not being ignored by the standard extraction procedure. How can I ignore them?
- All my STARE data are processed as individual files - how can I have them stacked by the pipeline?
- What is the meaning and use of the parameter UseResponseFlat in the FlatStrategy actor?
- The IFU slice object traces show a not negligible shift. How can I improve the corresponding object traces alignment?
- I activated the "Use CalSelector Associations" option in the DataOrganizer. Now I get an error even though the Datasets were marked as complete. Why?
- My NODDING data are not processed.
- My OFFSET data are not processed.
- Can I process OFFSET or NODDING mode data as STARE mode data?
- The response curve leaves residual instrument features in my science.
- My flux-calibrated data do not agree with independent photometric measurements.
- I cannot find flux standard stars with the same readout mode and binning as my science data.
- Why do I see only a few peaks in the three display windows that appear after running the xsh_respon_slit_<mode> recipe in Reflex?
- How can I improve the flux calibration of my spectra?
- The sky in my NIR SLIT STARE data is not well subtracted.
- Some of my extracted NIR STARE spectra show a jump at about 2.3μm - why and how can I correct it?
- I get inconsistent results from different absorption/emission lines in my NIR spectrum - why?
- How is the sky spectrum for OFFSET data produced?
- How can I improve the sky correction of my STARE data?
- Why are some of the sky lines in my STARE data not corrected at all?
- Is there an optimal extraction in nodding mode?
- How can I improve spectrum extraction?
- My extracted 1-dimensional NIR spectra show many spikes although the raw signal looks very good. What happened?
- Why does the extracted NODDING spectrum not change if I set localize-method to MANUAL and vary localize-slit-position?
- My spectrum of a bright source looks much noisier than I expected - why?
- What is the best way to reduce UVB/VIS NODDING data?
- The sky subtraction in my NODDING data is really bad - what could be the reason?
- My data have spatially variable sky background - how can I subtract it properly?
- My MERGE1D spectrum shows a gap although the MERGE2D spectrum does not.
- On the MERGE2D spectrum I see blobs with intensity zero. Why?
- How can I correct telluric absorption lines in the Reflex science end products?
General
Pipeline
Reflex workflow
Processing problems
Flux calibration
Sky correction and spectra extraction
Post-Processing