Data Reduction FAQ

If your question is not found below, please email your query to salthelp@salt.ac.za.

  1. Where can I find line lists for SALT spectra?
  2. Are filters curves available for the instruments?
  3. Are filters curves available for the instruments?
  4. Where can I find an extinction curve for Sutherland?
  5. What are those extra lines in my arc spectra?
  6. I used scisoft for my installation of pyraf. Can I install pysalt?
  7. saltprepare is not working, what’s the problem?
  8. How do I flat-field my data?
  9. What are those weird faint emission lines at unidentifiable wavelengths in my spectra?

1. Where can I find line lists for SALT spectra?

An arc atlas has been compiled here.

An alternative/additional atlas is also being put together here.

2. Are filters curves available for the instruments?

Yes, filters curves are available as part of the PySALT package in the data/ directory.  They are also available online: SALTICAM filter curves are available here and RSS filter curves are available here.

3. Are filters curves available for the instruments?

Yes, filters curves are available as part of the PySALT package in the data/ directory.  They are also available online: SALTICAM filter curves are available here and RSS filter curves are available here.

4. Where can I find an extinction curve for Sutherland?

An extinction curve is available as part of the PySALT package and is also available here.

5. What are those extra lines in my arc spectra?

We have had a range of issues with the lamps and the power supplies and have had to swamp lamps at times.   Some of the lamps show contamination and depending on the lamp you are using there may be additional lines.   For example, the Neon lamp shows contamination from Argon and the NeAr lines may provide a better fit.

6. I used scisoft for my installation of pyraf. Can I install pysalt?

We suggest using Macports for the installation of PySALT,  but if you did install pyraf using scisoft, it is still possible to install PySALT.

There can be several issues with the installation that are beyond the normal instructions:

1. PyRAF installed by scisoft uses a version of python that it installs.  So additional packages which you install must use either the scisoft python, the site-package location for this python or you must add the location for the installation to the PYTHONPATH for this python.

2. The installation of PyQT can be tricky when not using the framework python.  Some suggested options to set can be found herehere, and here, but installation can depend on the system.  The PyQT message form can also be helpful for possible solutions to your specific problem with PyQT installation.

3. If this still doesn’t help, please email salthelp@salt.ac.za.  If you do find something that works for your system, please add details to the science wiki directions for installation.

7. saltprepare is not working, what’s the problem?

If the images being written out by saltprepare (or any other task) are corrupted, please check the version of pyfits you are using. This can done by typing:

python -c ‘import pyfits; pyfits.__version__’

If the version is 3.0, then the problem is with the version of pyfits that you are using. Please upgrade to the newest version.

If this does not solve the problem, please shoot an email to salthelp@salt.ac.za

8. How do I flat-field my data?

Please see this page on the SALT science wiki.

9. What are those weird faint emission lines at unidentifiable wavelengths in my spectra?

If you have bright stars on the slit you may be more prone to Littrow Ghost reflections. According to this paper on the issue, these are usually at a fixed position and around 1E-4 fainter than the star causing them. While most common on RSS longslit spectra, they can also appear in RSS MOS observations, so special care should be taken not to confuse them with real emission line objects!