To: Benjamin,
RE:"Comparing line's strength/intensity from spectra with different resolution leads to a wrong diagnostic.
The more the resolution power RP is high, deeper line are."
Quite right, I tweaked my condenser lens and got a bite higher resolution on my 13Jan2020 and compared:
But to answer what you correctly quoted Francois on the more important feature to study, the Effective line width (EW) in this case Ha, I cropped
these between 6558.4A and 6568.9A and produced a chart that makes measuring the EW a little easier:
I took this into PS and did my best to measure equal areas within the Ha region that comprise the EW; see:
Trial#1, 09Jan19 for H-alpha EW= 3.09A / Trial#1, 13Jan20 for H-alpha EW= 3.08A
Trial#2, 09Jan19 for H-alpha EW= 2.94A / Trial#2, 13Jan20 for H-alpha EW= 2.95A
Diff: EW(09Jan19)-EW(13Jan20)= +0.01A Trial#1
Diff: EW(09Jan19)-EW(13Jan20)= -0.01A Trial#2
Average= 0.00A
Basically, these measurements say is there has been no noticeable change in over a year in a Orion's H-alpha EW at the resolution we can see with the LhiresIII.
Basically all I can say with these Telluric (not RV) calibrated H-alpha spectra of a Orion is that the 13Jan20 Ha line is shifted towards the UV with respect
to the 09Jan19 Ha line; note that these were not radial velocity corrected. Let me know if you have anything else helpful to add!
James