Details

Type: Bug

Status: To Do

Resolution: Unresolved

Fix Version/s: None

Component/s: afw, obs_subaru

Labels:

Story Points:4

Team:Architecture
Description
The calculations of hour angle and parallactic angle in VisitInfo.cc use getBoresightRaDec(), which returns Ra and Dec in the International Celestial Reference System (ICRS). However, the correct frame for those calculations is the Celestial Intermediate Origin (CIO, or cirs in Astropy). Using the wrong coordinate frame ignores precession and nutation. It is probably correct to store the boresight RA and Dec coordinates in ICRS, but they need to be transformed to CIO for the hour angle and parallactic angle calculations.
I think it's also possible that we need to apply an additional correction because we are using earth rotation angle and not local sidereal time.