Fill in HSC VisitInfo boresightRotAngle

Uses the formula
boresightRotAngle = 270 - INST-PA
where INST-PA is the position angle from the HSC file header.
Also sets rotType to rotType.SKY.

python/lsst/obs/hsc/makeHscRawVisitInfo.py

@@ -27,17 +27,14 @@
 
 from lsst.afw.geom import degrees
 from lsst.afw.coord import Coord, IcrsCoord, Observatory, Weather
+from lsst.afw.image import RotType
 from lsst.obs.base import MakeRawVisitInfo
 
 __all__ = ["MakeHscRawVisitInfo"]
 
 
 class MakeHscRawVisitInfo(MakeRawVisitInfo):
     """Make a VisitInfo from the FITS header of a Subaru HSC image
-
-    Boresight rotation angle could probably be set from one of:
-    - INST-PT (but apparently only available for HSC, not suprimecam)
-    - INR-TR, INR-END (but appears to not be SKY; so probably not interesting)
     """
     observatory = Observatory(-155.476667*degrees, 19.825556*degrees, 4139)  # long, lat, elev
 
@@ -67,6 +64,12 @@ def setArgDict(self, md, argDict):
         argDict['era'] = self.eraFromLstAndLongitude(LST, self.observatory.getLongitude())
         argDict['darkTime'] = argDict['exposureTime']
 
+        # Rotation angle formula determined empirically from visual inspection
+        # of HSC images.  See DM-9111.
+        rotAngle = (270.0*degrees - self.popAngle(md, "INST-PA")).wrap()
+        argDict['boresightRotAngle'] = rotAngle
+        argDict['rotType'] = RotType.SKY
+
     def getDateAvg(self, md, exposureTime):
         """Return date at the middle of the exposure
 

tests/testRepository.py

@@ -103,8 +103,8 @@ def setUp(self):
         self.boresightRaDec = IcrsCoord('21:22:59.982', '+00:30:00.07')
         self.boresightAzAlt = Coord(226.68922661*degrees, 63.04359233*degrees)
         self.boresightAirmass = 1.121626027604189
-        self.boresightRotAngle = float("nan")*degrees
-        self.rotType = RotType.UNKNOWN
+        self.boresightRotAngle = 270.0*degrees
+        self.rotType = RotType.SKY
         self.obs_longitude = -155.476667*degrees
         self.obs_latitude = 19.825556*degrees
         self.obs_elevation = 4139
@@ -134,7 +134,7 @@ def testRaw(self):
         self.assertCoordsNearlyEqual(visitInfo.getBoresightRaDec(), self.boresightRaDec)
         self.assertCoordsNearlyEqual(visitInfo.getBoresightAzAlt(), self.boresightAzAlt)
         self.assertAlmostEqual(visitInfo.getBoresightAirmass(), self.boresightAirmass)
-        self.assertTrue(math.isnan(visitInfo.getBoresightRotAngle().asDegrees()))
+        self.assertAnglesNearlyEqual(visitInfo.getBoresightRotAngle(), self.boresightRotAngle)
         self.assertEqual(visitInfo.getRotType(), self.rotType)
         self.assertEqual(visitInfo.getExposureTime(), self.exptime)
         self.assertEqual(visitInfo.getDarkTime(), self.darktime)