[daip] New Ticket - [!RWG-256174]: COPIX and 0 declination

[Michael Bietenholz]

New Ticket: COPIX and 0 declination

COPIX has an ambiguity if decl = 0d.

If I run COPIX w/ OPTY='PIXE' on a pixel with say, decl = +0d 1' 2", then returns COORDINA= x,x,x,0,1,2. 

So far so good.  But now if I run COPIX on a pixel with decl = -0d 1' 2", then COPIX returns exactly the same values of COORDINA.

I see from EXPLAIN COORDINA that it actually just represents the absolute values of the coordinates, and the decl is -ive if any of the three relevant array elements is -ive.   According to "EXPLAIN COORDINA", if any one of the declination values is -ive that implies a southerly declination, so COPIX should be returning COORDINA = 0,-1,+-2..

Also, if COPIX is run in the other direction to say find the pixel coords some pixel at decl -0d 1' 2", most users would probably just type COORDINA = x x x, -0, 1, 2, which would of course produce the coordinates of decl = +0,1,2.  It might be good to add a note in the COPIX saying that in the case of -ive declinations north of -1d you have to make sure that COPIX(5) is -ive. 

Ticket Details
===================
Ticket ID: RWG-256174
Department: AIPS Data Processing
Priority: Default
Status: Open
Link:  https://help.nrao.edu/staff/index.php?_m=tickets&_a=viewticket&ticketid=2179