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#### 5.3.1 `skysim`

Usage: `:skysim:<nrow>`

Generates a simulated all-sky star catalogue with a specified number of rows. This is intended to provide crude test catalogues when no suitable real dataset of the required size is available. In the current implementation the row count, which may be given in integer or exponential notation, is the only parameter, so the specification "`:skysim:5e6`" would give a 5 million-row simulated catalogue.

The current implementation provides somewhat realistic position-dependent star densities and distributions of magnitudes and colours based on positionally averaged values from Gaia EDR3. The source positions do not correspond to actual stars. The columns and the statistics on which the output is based may change in future releases.

Example:

    :skysim:6
    +-----------+------------+------------+------------+-----------+-----------+------------+
    | ra        | dec        | l          | b          | gmag      | rmag      | b_r        |
    +-----------+------------+------------+------------+-----------+-----------+------------+
    | 266.7702  | -32.689117 | -3.044958  | -2.217145  | 18.168278 | 16.03555  | 1.046624   |
    | 276.83398 | 8.132022   | 37.491447  | 9.031909   | 18.331224 | 18.786451 | 1.4425725  |
    | 92.04118  | 23.79857   | -173.02219 | 1.7854756  | 16.743847 | 15.623316 | 1.690048   |
    | 271.08215 | -5.2012086 | 22.848532  | 8.022958   | 21.538874 | 17.782997 | 2.1645386  |
    | 298.83368 | 31.401922  | 67.75605   | 1.6348709  | 20.145718 | 17.728764 | 1.1521724  |
    | 204.9299  | -77.07571  | -54.29949  | -14.464215 | 19.044079 | 20.277771 | 0.92987275 |
    +-----------+------------+------------+------------+-----------+-----------+------------+

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STILTS - Starlink Tables Infrastructure Library Tool Set
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