http://www.spectro-aras.com/forum/viewt ... =70#p16741
Hi Olivier2SPOT wrote:
And comparison between ISIS and spec inti process, better resolution and better snr in the blue part of the spectrum because of the way to calibrate the spectrum on each raw image with the [OI] atmospherique line at 5577,35Å with a new method to apply the flat.
That is an interesting comparison. Why is the continuum different in the red? There should of course be no difference on the same data. Do you know why? The big question is Which is "right" ?
I am also surprised at the noise at the blue end even at 4000A (due to the flat?). I tested this last year with using my ALPY and ISIS with and without a flat and found less than 1% additional noise from 3800-7800A using a master flat made from a stack of 30 well exposed flats.
Cheers
Robin