This follows on from Andrew’s post about needing to recalibrate his CCDSPEC/QHY6 when he changed image acquisition software from Nebulosity 4 to EZCAP:
Regarding why recalibration is necessary when image acquisition software is changed:
It’s quite simple really.
Although the spectrum appears in exactly the same location on the chip, what comes out depends on how he data is clocked out and that depends on the software. Some chips have non sensitive pixels which are clicked out first and disregarded whilst other programs read out the whole chip which may be bigger than the imaging part.
So the pixel number in both X and Y can be different. Hence, it is essential to do the calibration and observations with the same readout program
Hope this helps.
PS I designed and built a CCD camera Electronics and software 30 years ago