11.6 Examples

1. This template file will create a 200 x 300 pixel image, with 4-byte integer pixel values, in the primary HDU:

  SIMPLE = T
  BITPIX = 32
  NAXIS = 2     / number of dimensions
  NAXIS1 = 100  / length of first axis
  NAXIS2 = 200  / length of second axis
  OBJECT = NGC 253 / name of observed object

The allowed values of BITPIX are 8, 16, 32, -32, or -64, representing, respectively, 8-bit integer, 16-bit integer, 32-bit integer, 32-bit floating point, or 64 bit floating point pixels.

2. To create a FITS table, the template first needs to include XTENSION = TABLE or BINTABLE to define whether it is an ASCII or binary table, and NAXIS2 to define the number of rows in the table. Two template lines are then needed to define the name (TTYPEn) and FITS data format (TFORMn) of the columns, as in this example:

  xtension = bintable
  naxis2 = 40
  ttype# = Name
  tform# = 10a
  ttype# = Npoints
  tform# = j
  ttype# = Rate
  tunit# = counts/s
  tform# = e

The above example defines a null primary array followed by a 40-row binary table extension with 3 columns called 'Name', 'Npoints', and 'Rate', with data formats of '10A' (ASCII character string), '1J' (integer) and '1E' (floating point), respectively. Note that the other required FITS keywords (BITPIX, NAXIS, NAXIS1, PCOUNT, GCOUNT, TFIELDS, and END) do not need to be explicitly defined in the template because their values can be inferred from the other keywords in the template. This example also illustrates that the templates are generally case-insensitive (the keyword names and TFORMn values are converted to upper-case in the FITS file) and that string keyword values generally do not need to be enclosed in quotes.