***Copy of 00README_errspec_create from EmissionLineComp/ because I basically copied this procedure here except that I started from the fracerrspec_dsp* files and then made and used an adderrspec*.sm macro for each template.***

OK, I created the error spectra in a somewhat random way.  They were
actually created and added with the SM macro adderrspec.sm.

I started with an actual data and error spectrum of an SDSS object
(SDSS0245 from my SDSSvMODSCIVmasses/SDSSspectra/ directory), and
divided the two to get a fractional uncertainty spectrum. The mean for
this particular fractional error spectrum is 0.223, which is kind of
high for the S/N in a lot of our spectra that we have.  I will therefore
modify this based on the S/N I imposed in the spectra, such that the
mean fractional error for any given degraded spectrum is ~1/(S/N).

This won't be entirely realistic, since it will matter what the actual
wavelength range of any given spectrum is (i.e., noise spikes due to
imperfect sky subtraction won't be at real locations of sky lines...),
compared to this one, but at least it'll give realistic type bumps and
wiggles.

Next to get it to cover the respective ranges of my fake data, I
resampled it to the different dispersions I selected for the fake data,
also making it the correct length as each of the fake spectra, and then
multiplied it by first the factor to make the mean fractional
uncertainty match the S/N and then by the spectrum itself.

For the one spectral range that was longer than the SDSS spectrum, I
just repeated it backwards, which is totally dodgey, I know...  But it
at least gives us something right now.

Here's me making the various resampled spectra in pyraf:
--> rspectext sdss_frac_errorspec.dat sdss_frac_errorspec.fits
--> epar dispcor
--> dispcor sdss_frac_errorspec.fits fracerrspec_dsp1p0.fits
sdss_frac_errorspec.fits: Resampling using current coordinate system
fracerrspec_dsp1p0.fits: ap = 1, w1 = 3788., w2 = 9202., dw = 1., nw = 5415
--> epar dispcor
--> dispcor sdss_frac_errorspec.fits fracerrspec_dsp1p25.fits
sdss_frac_errorspec.fits: Resampling using current coordinate system
fracerrspec_dsp1p25.fits: ap = 1, w1 = 3800., w2 = 9202.5, dw = 1.25, nw = 4323
--> epar dispcor
--> dispcor sdss_frac_errorspec.fits fracerrspec_dsp2p0.fits
sdss_frac_errorspec.fits: Resampling using current coordinate system
fracerrspec_dsp2p0.fits: ap = 1, w1 = 3788., w2 = 9202., dw = 2., nw = 2708
--> epar dispcor

Task dispcor is running...

sdss_frac_errorspec.fits: Resampling using current coordinate system
fracerrspec_dsp0p12448.fits: ap = 1, w1 = 3790.386, w2 = 9202.403, dw = 0.12448, nw = 43478
--> epar dispcor

Task dispcor is running...

sdss_frac_errorspec.fits: Resampling using current coordinate system
fracerrspec_dsp0p25.fits: ap = 1, w1 = 3800., w2 = 9202.5, dw = 0.25, nw = 21611
--> epar dispcor

Task dispcor is running...

sdss_frac_errorspec.fits: Resampling using current coordinate system
fracerrspec_dsp3p0.fits: ap = 1, w1 = 3800., w2 = 9203., dw = 3., nw = 1802


Everything else was done in the SM macro using these pyraf output as input.