Data Reduction Frequently Asked Questions
List of FAQs
The search will be performed in the questions and answers.
- 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"?
- 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?
- 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?
- 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?
- 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?
- 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?
- 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?
- 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?
- 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?
- 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?
Spectroscopy - Flux Calibration
Spectroscopy - Sky Subtraction and Spectra Extraction
- 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?
- 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?
- Are there any known problems with VIMOS data?
- What is the best way to reduce VIMOS data?
- 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?
- Setting skyalign to values of 0 or higher has no effect on my results. Why?
- How can I be sure that my fibres are correctly labeled?
- VISIR (pre-upgrade)
- 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.
- Are there any known problems with X-Shooter data?
- What is the best way to reduce X-Shooter data?
- Are there order definition frames with spatial information, i.e. using 9 pinholes instead of 1?
- How can I find acquisition camera skyflats?
- There are 2 possibilities of data reduction: the polynomial and the physical mode, which one should I use?
- 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?
- Where can I find reference file of tag "XSH_MOD_CFG_TAB_VIS" which is required as an input for xsh_util_physmod?
- Why are there three arc line catalogs for each arm?
- All my STARE data are processed as individual files - how can I have them stacked by the pipeline?
- We didn't find a parameter in the Reflex workflow to switch on the production of the flux calibrated sky spectrum.
- The reduced science spectrum displayed in the Reflex window appears good but when I try to plot it, it is quite different. How can I get it?
- Why do the flats in my data have different exposure times and how do I know which ones to use?
- 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?
- 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.
- How is the sky spectrum for OFFSET data produced?
- How can I improve the sky correction of my STARE data?
- Is there an optimal extraction in nodding mode?
- How can I improve spectrum extraction?
- 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?
Sky correction and spectra extraction