cross

cross cross-matches two FITS tables by position.

Each row of the second table gets the nearest row of the first, if it lies within --tol. Use it to match two catalogues (e.g. from cone), or a catalogue with the PHOTOMETRY table of a calibrated frame. The result is a table of row indices, not a merged table. cross works offline.

Usage

munipack cross --tol DEG [options] file1 file2

Each file is read from its first table extension. Choose another one with the CFITSIO syntax, e.g. 'frame_cal.fits[PHOTOMETRY]'.

Options

Option	Default	Description
--tol deg	near zero	Match radius; always give it (the default matches nothing), e.g. 3e-4 (about 1″).
--col-ra col1,col2	RA,RA	RA columns of file1 and file2; give both names.
--col-dec col1,col2	DEC,DEC	Dec columns of file1 and file2; give both names.
--col-pm-ra col1,col2	—	Proper motion in RA (mas/yr); do not use, see below.
--col-pm-dec col1,col2	—	Proper motion in Dec (mas/yr); do not use, see below.
--col-epoch-ra column	—	Accepted but ignored.
--col-epoch-dec column	—	Accepted but ignored.
--col-mag col1,col2	—	Magnitude columns; not used by the match.
--ftol ratio	1	Flux tolerance; not used by the match.
--vocat file	—	Accepted but ignored.
-o, --output file	cross.fits	Output file (overwritten).
--verbose	off	Verbose messages.
-h, --help	—	Show the help.

Warning

The proper-motion correction is broken in this version and spoils the match of cone tables. Leave out --col-pm-ra and --col-pm-dec; astrometry and phcal apply proper motions themselves.

Output

The output table CROSSMATCH has two columns of 1-based row numbers: for each row of file2, the matching row of file1, and vice versa (0 means no match).

Examples

UCAC4 against Gaia DR3 over the same field:

munipack cross --tol 3e-4 --col-ra RAJ2000,RA_ICRS --col-dec DEJ2000,DE_ICRS \
    -o ucac4_gaia.fits ucac4.fits gaia.fits

The stars of a calibrated frame against the reference catalogue:

munipack cross --tol 3e-4 --col-ra RAJ2000,RAJ2000 --col-dec DEJ2000,DEJ2000 \
    -o matched.fits 'frame_cal.fits[PHOTOMETRY]' ucac4.fits

Notes

• The match is not strictly one-to-one: two close stars in one table can both pick the same star in the other.