High resolution X-ray spectroscopy with the diffraction gratings of Chandra and XMM-Newton offers new chances to study a large variety of stellar coronal phenomena .
A popular X-ray calibration target is Capella , which has been observed with all gratings with significant exposure times .
We gathered together all available data of the HETGS ( 155 ks ) , LETGS ( 219 ks ) , and RGS ( 53 ks ) for comparative analysis focusing on the Ne ix triplet at around 13.5 Å , a region that is severely blended by strong iron lines .
We identify 18 emission lines in this region of the HEG spectrum , including many from Fe xix , and find good agreement with predictions from a theoretical model constructed using the Astrophysical Plasma Emission Code ( APEC ) .
The model uses an emission measure distribution derived from Fe xv to Fe xxiv lines .
The success of the model is due in part to the inclusion of accurate wavelengths from laboratory measurements .
While these 18 emission lines can not be isolated in the LETGS or RGS spectra , their wavelengths and fluxes as measured with HEG are consistent with the lower resolution spectra .

In the Capella model for HEG , the weak intercombination line of Ne ix is significantly blended by iron lines , which contribute about half the flux .
After accounting for blending in the He-like diagnostic lines , we find the density to be consistent with the low density limit ( n _ { e } < 2 \times 10 ^ { 10 } cm ^ { -3 } ) ; however , the electron temperature indicated by the Ne ix G -ratio is surprisingly low ( \sim 2 MK ) compared with the peak of the emission measure distribution ( \sim 6 MK ) .
Models show that the Ne ix triplet is less blended in cooler plasmas and in plasmas with an enhanced neon-to-iron abundance ratio .