FAQ

Why isn’t autoidentify putting the arc lines in the right place? Why is my wavelength solution bad?

Are the crval and cdelt values appropriate for the CCD, grating, and angle you’re using? The check_gratings_angles() function attempts to automatically determine the correct values, but it is not foolproof.

You can use this calculator to determine approximate crval (center wavelength in angstroms) and cdelt values (disperson in Angstroms/pixel) for your grating. Input the grating and side you are using and a guess for the center wavelength; click calculate and note the reported grating angle. Edit your center wavelength guess until you find your grating angle. The calculator then gives the center wavelength and dispersion you want.

reset to new values with:

det_pars['red']['crval'] = 7330
det_pars['red']['cdelt'] = 3.022

I don’t have any 0.5” slit arcs–what can I do?

Choose another slit width and set it as the default:

# use 1.0 arcsecond slit for arcs
create_arc_dome(arcslit='1.0')

# set default arc files
det_pars['blue']['arc']  = 'FeAr_1.0.fits'
det_pars['red']['arc']  = 'HeNeAr_1.0.fits

I’m getting "ERROR (1, "image keyword AIRMASS not found")" when I run create_arc_dome().

One of your images is missing a header keyword–find it and mark it bad.

I’m not happy with the fluxing–what can I do?

Run iraf.sensfunc() and tweak to test, then repeat your extract1D() call.

During fluxing, iraf.calibrate crashes and says it can’t find sens-blue.0001.fits. (or sens-red)

You can work around this by symlinking sens-blue.fits to sens-blue.0001.fits:

ln -s sens-blue.fits sens-blue.0001.fits

Is there any way to reduce the repetive prompting?

pyraf-dbsp comes with a modified doslit version that minimizes prompting.However, it seems to cause iraf errors for some users. To run it, set

export USEDBSPDOSLIT=1

before starting ipython.

I’m getting an error:

ERROR: An unexpected error occurred while tokenizing input
The following traceback may be corrupted or invalid
The error message is: ('EOF in multi-line statement', (11, 0))

File "<tokenize>", line 2
    if (Vars.dispcor and Vars.fluxcal1):
IndentationError: unindent does not match any outer indentation level

This error is mysterious; it pops up irregularly, particularly if a routine has aborted unnaturally. Try restarting ipython and running your command again, but be aware that in some cases it may be necessary to wipe the directory and restart from the raw images.