Aligning echelle grisms, slits and cross dispersers
As the Echelle orders appear very curved on the chip, and as the
Echelle slits are very short, there is no real reason for aligning any
However, it is important to define the
center of the slitlet in the
file (use alfosc.edit-slitpos).
The position of slit center (in CCD pixel coordinates) must be
measured from a unbinned full-frame slit image, without a
filter in the ALFOSC beam. Use the ThAr lamp with 0.2 sec
Here the link to the infamous obsolete instructions.