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`sky3d`

: Spherical Polar Matching

matcher=sky3d values*='<ra/deg> <dec/deg> <distance>' params='<error/units of distance>' tuning='<bin-factor>'

`values*`

:

`ra/deg`

: Right Ascension`dec/deg`

: Declination`distance`

: Distance from origin`params`

:

`error/units of distance`

: Maximum Cartesian separation for match`tuning`

:

`bin-factor`

: Scaling factor to adjust bin size; larger values mean larger bins

The `sky3d`

matcher compares positions in the volume of
the sky taking account of distance from the observer.
The position in three-dimensional space is calculated for each
row using the `ra`

, `dec`

and `distance`

as spherical polar coordinates, where `distance`

is the
distance from the observer along the line of sight.
Rows are considered to match when their positions in this space are
within `error`

units of each other.
The units of `error`

are the same as those of
`distance`

.

As with `sky`

matching,
other longitude/latitude coordinate pairs may be used in place of
right ascension and declination.

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Starlink User Note256

STILTS web page: http://www.starlink.ac.uk/stilts/

Author email: m.b.taylor@bristol.ac.uk

Mailing list: topcat-user@jiscmail.ac.uk