skyerr: Sky Matching with Per-Object Errors
matcher=skyerr values*='<ra/degrees> <dec/degrees> <error/arcsec>' params='<scale/arcsec>' tuning='<healpix-k>'
ra/degrees: Right Ascension
error/arcsec: Per-object error radius along a great circle
scale/arcsec: Rough average of per-object error distance; just used for tuning to set default pixel size
healpix-k: Controls sky pixel size. Legal range 0 - 29. 0 is 60deg, 20 is 0.2".
skyerr matcher compares positions on the celestial
sphere using error radii which can be different for each row.
Rows are considered to match when the separation between the
dec positions is no larger than
the sum of the two per-row
scale parameter should be a rough average value
of the error distances. It is used only to set a sensible default for
healpix-k tuning parameter, and its value does not affect
the result. If you set
healpix-k directly, its value is ignored.
other longitude/latitude coordinate pairs may be used in place of
right ascension and declination.
Note: the semantics of this matcher have changed
slightly at version 2.4 of STILTS.
In earlier versions the single parameter was named
and provided an additional constraint on the maximum accepted separation
between matched objects. For most uses, the old and new behaviours are
expected to give the same results, but in cases of difference, the new
behaviour is more likely what you want.