[fitswcs] Long-slit spectroscopy WCS

[Malcolm J. Currie]

I just want to check that my understanding of the proposed long-slit
WCS for an arbitrary position angle.  The examples I've seen only show
the slit aligned along Right Ascension.

For an arbitrary position angle, is it merely a question of computing
the components of the spatial increments along the slit, and assigning
them to CDELT2 and CDELT3?

Malcolm