b) even after we fixed the rotation using msctpeak and mscsetwcs, there were
very bad (1.5" peak-to-trough), higher order wiggles.
We fixed this by fitting the higher order terms
with msctpeak (going to order 4) and making sure the projection was tnx,
then runnig mscsetwcs and checking again with msctpeak.
Along the way I believe we discovered a bug in msctpeak, in which
the ":rotate " parameter in fact does NOT rotate the expected coordinates
around the center of Mosaic correctly; it looked like assumed rotation axis
was somewhere else. This meant that we had to do an endless number of
"l...l" within msctpeak to get stars and expected positions to match."
Parameters for MSCtpeak:
PACKAGE = mscfinder
TASK = msctpeak
images = obj1043 List of WCS calibrated Mosaic images
coordina= N6822.usno List of ra(hr), dec(deg), optional id
database= N6822.db Database for astrometric fit
(extname= ) Extensions
(epoch = 2000.) Coordinate epoch
(update = yes) Update image header WCS following fit?
(autocen= no) Center catalog coords when entering task?
(boxsize= 9) Centering box fullwidth
(project= tnx) Sky projection geometry
(fitgeom= general) Fitting geometry
(functio= polynomial) Surface type
(xxorder= 4) Order of xi fit in x
(xyorder= 4) Order of xi fit in y
(xxterms= half) Xi fit cross terms type
(yxorder= 4) Order of eta fit in x
(yyorder= 4) Order of eta fit in y
(yxterms= half) Eta fit cross terms type?
(reject = 3.) Rejection limit in sigma units
(interac= yes) Enter interactive image cursor loop?
(frame = 1) Display frame number
(marker = circle) Marker type
(omarker= plus) Overlay marker type
(goodcol= blue) Color of good marker
(badcolo= red) Color of bad marker
(fdimage= )
(fdcoord= )
(mode = q)
PACKAGE = mscred
TASK = mscsetwcs
images = obj* Mosaic images
database= N6822.db WCS database
(ra = ra) Right ascension keyword (hours)
(dec = dec) Declination keyword (degrees)
(equinox= equinox) Epoch keyword (years)
(ra_offs= 0.) RA offset (arcsec)
(dec_off= 0.) Dec offset (arcsec)
(extlist= )
(mode = ql)