It is interesting to estimate the net difference in flux between Marc’s and Jack’s setup. (A C11 with a 35um slit compared with a C14 with a 23um slit.) at 3 arcsec the slit throughput is 70% and 40% respectively but because of the higher collecting area of the C14 the difference in flux is reduced. The net effect is the total flux after the slit should be quite similar (Jack’s is ~5 % lower) Jack’s resolution will be ~50% higher though because of the narrower slit.
A good estimate of the actual resolution can be made from the FWHM of the internal calibration lamp lines.
Robin