Hi Ken,
After a bit of work and reading over the last few days, I've come across this info in
Analysis and Interpretation of Astronomical Spectra By Richard Walker, pg 25 of 90;
For correction curves, obtained this way, the familiar term instrumental response" is misleading.
This curve doesn’t just reflect the erroneous recording characteristics of the spectrograph, camera and telescope, but also the
wavelength dependent filtering effect of the Interstellar Matter and of the Earth's atmosphere. Strongly different spectral classes with distinctly different temperatures must therefore inevitably generate strongly different correction curves. Therefore the often postulated “all purpose use” of just one single correction curve causes strong errors, if used for other spectral classes.
After a number of runs through VSpec, it seems the only way to get my curves to match up with the relevant library curves, is through the use of slightly different instrument response curves.
Does this make sense to you? Mark